Please! Need help deciding an efficient Pc.

Hmm...
I recommend you build your own PC. Going through a company to get the PC adds a lot of service cost and pretty much shackles you to their tech support if something ever goes wrong. The kind of PC your looking for, they arent really the ones to provide it either, they'l sell you a $4000 computer that's no better than what you could make yourself for $2500 (for your purposes)
Parts to pick, if you want I could come up with a build that's suitable for you. Actually building it, its LEGO for adults, if you know squares go into square holes and can read instruction manuals, you can build a computer.

My advice, your budget of $4000 is way more than you need for what your after. Your looking for a gaming rig that can also act as a hobbyist work-station, something like that is definitely possible on $2000.

Hey Buddy,
I wish to tell u something. Do not go for custom built pcs like Origin PC etc. First, since u r new to pcs, u dont need a $4000 pc. First lets start off with a $1000 pc. Trust me dude! Dont go for very high end and complicated stuff without knowing about computers, overclocking and stuff. Heres a good build : http://pcpartpicker.com/p/3HYkH

PCPartPicker part list: http://pcpartpicker.com/p/3HYkH
Price breakdown by merchant: http://pcpartpicker.com/p/3HYkH/by_merchant/
Benchmarks: http://pcpartpicker.com/p/3HYkH/benchmarks/

CPU: Intel Core i5-4670 3.4GHz Quad-Core Processor ($209.29 @ Amazon)
Motherboard: ASRock H87M Pro4/ASM Micro ATX LGA1150 Motherboard ($96.97 @ Newegg)
Memory: G.Skill Sniper 8GB (2 x 4GB) DDR3-1600 Memory ($74.98 @ OutletPC)
Storage: Samsung 840 Pro Series 256GB 2.5" Solid State Disk ($199.98 @ OutletPC)
Storage: Western Digital BLACK SERIES 1TB 3.5" 7200RPM Internal Hard Drive ($79.98 @ OutletPC)
Video Card: EVGA GeForce GTX 760 2GB ACX Video Card ($249.99 @ Amazon)
Case: Fractal Design Define Mini MicroATX Mini Tower Case ($84.99 @ Newegg)
Power Supply: XFX 550W 80+ Bronze Certified ATX Power Supply ($47.99 @ NCIX US)
Total: $1044.17
(Prices include shipping, taxes, and discounts when available.)
(Generated by PCPartPicker 2014-05-11 11:54 EDT-0400)

This build can give u very high-ultra gaming on like most games on a single monitor at 1080p resolution for like 2-3 years. For now, i recommend u to buy this build. Before u buy a better premium build, learn about pc, gaming, overclocking, crossfire, sli and more other stuff and get used to it. Then u can buy a superb gaming pc that u wish to buy. A nice pc which suits ur needs. U wont be disappointed if u go with this build. If theres anything wrong, feel free to comment back.

And another thing i wanted to say. Laptops are pieces of crap when compared to a gaming pc. Please forget about laptops atleast until 2015 (coz thats when intel broadwell which has almost the same power of a desktop launches and will be available on laptops)

Hmm...
U cant play watchdogs on ultra, but u can play it on high or very high. Games like AC 4 BF, GTA V can be played on very high to ultra. Please dont ever compare this pc to a console again. Even this pc eats consoles for dinner. If u want like even high end, ill recommend u a build that can play like every single thing maxed out. OK?? But thats gonna cost a little bit. Before we move on to the pc build, ill let u know a few things about sli and crossfire. I totally dont recommend sli or crossfire. One powerful graphics card (gpu) is better than two less powerful graphics cards even when two gpus cost higher. Two gpus consume a lot of power, leads to uneven temperature distribution, lesser frame rates in some games, micro-stuttering (I think both companies have eliminated this hurdle now), etc. U can have two or more gpus in sli or crossfire if u want the most powerful pc or so like that.
OK, now heres the build:
http://pcpartpicker.com/p/3I0Qq

PCPartPicker part list: http://pcpartpicker.com/p/3I0Qq
Price breakdown by merchant: http://pcpartpicker.com/p/3I0Qq/by_merchant/
Benchmarks: http://pcpartpicker.com/p/3I0Qq/benchmarks/

CPU: Intel Core i7-4770K 3.5GHz Quad-Core Processor ($334.98 @ Best Buy)
CPU Cooler: Corsair H80i 77.0 CFM Liquid CPU Cooler ($74.99 @ Newegg)
Thermal Compound: Arctic Silver 5 High-Density Polysynthetic Silver 3.5g Thermal Paste ($6.98 @ OutletPC)
Motherboard: Asus Maximus VI Gene Micro ATX LGA1150 Motherboard ($193.78 @ OutletPC)
Memory: G.Skill Sniper 8GB (2 x 4GB) DDR3-1600 Memory ($74.98 @ OutletPC)
Storage: Samsung 840 Pro Series 256GB 2.5" Solid State Disk ($199.98 @ OutletPC)
Storage: Western Digital BLACK SERIES 1TB 3.5" 7200RPM Internal Hard Drive ($79.98 @ OutletPC)
Video Card: Asus GeForce GTX 780 Ti 3GB DirectCU II Video Card (2-Way SLI) ($689.99 @ Amazon)
Video Card: Asus GeForce GTX 780 Ti 3GB DirectCU II Video Card (2-Way SLI) ($689.99 @ Amazon)
Case: Corsair 350D Window MicroATX Mid Tower Case ($88.98 @ Newegg)
Power Supply: Corsair RM 850W 80+ Gold Certified Fully-Modular ATX Power Supply ($139.99 @ Amazon)
Optical Drive: Asus DRW-24B1ST/BLK/B/AS DVD/CD Writer ($19.98 @ OutletPC)
Operating System: Microsoft Windows 8.1 (OEM) (64-bit) ($89.98 @ OutletPC)
Monitor: Asus PB278Q 27.0" Monitor ($482.99 @ NCIX US)
Case Fan: Corsair Air Series AF120 Quiet Edition (2-Pack) 39.9 CFM 120mm Fans ($24.15 @ NCIX US)
Keyboard: Corsair Vengeance K70 Wired Gaming Keyboard ($107.99 @ Amazon)
Mouse: Logitech G9x Wired Laser Mouse ($77.98 @ SuperBiiz)
Total: $3377.69
(Prices include shipping, taxes, and discounts when available.)
(Generated by PCPartPicker 2014-05-11 13:18 EDT-0400)

I've suggested u an unlocked processor which can be overclocked. Bcoz games like watch dogs needs a powerful processor. Ive also suggested a 1440p monitor bcoz it is really a beastly pc. Although it is micro-atx, it has all the features of an atx board. I suggested u a sli build bcoz the gtx 780 ti is a very powerful graphics card. U cant ask for more. Two gtx 780 tis can do anything. U can even have a single gtx 780 ti but make sure u get one in the future or buy a 650 W PSU instead of 850 W. Dont worry of the risk of overclocking and all. Watch many youtube videos on how to overclock. Overclocking is actually easy but it is a little dangerous, i.e. u should'nt make any error in that. U should be careful while ocing. If u dont ever wish to oc, then ur better buy the i7 4770. Coming to the keyboard, mechanical keyboards are the best for gaming. If u dont wish to spend much, u could just use a normal one. Select any keyboard, mouse, os etc that u think would be nice. Just dont spend much in any other keyboard other than mechanical keyboard. If u dont like this build, please say to me..

Edit : U can even add (2x8) 16 gb of gskill sniper coz this is a very powerful gaming pc. And also, u can have a 1080p triple monitor setup if u need it.

Case fans come with the case itself, I tend to not add fans to a build until after I have made it. Fans can get expensive, no need to buy them if you dont really need them, which is often the case.
That card has the strongest single GPU performance on the market right now, chances are you could get maximum settings at 1440p with a few compromises on frame rate and lesser settings like AA.
You can have a maximum of two cards in the build.
Optical drive should be compatible, just throw one in as they don't really matter anymore.

Charanjit's build, tbh it looks like he has just ramped up the expense for not much gain. In terms of video editing performance, its worse off than mine (8GB vs 16GB) and gaming is already covered unless your going after a triple screen or 4K setup.
Triple screen setups are pretty awesome, I have one and its great for productivity. That sheer amount of desktop real estate means you can have near everything open at once at a good size. Ever had the situation where your writing an essay and constantly tabbing between Word and your research, and to give each half the screen means that its a horrible experience for both? Multiple monitors alleviates that. If you have three monitors (need to be identical on Nvidia) you can also game across the three of them.

Sound cards, or at least expensive ones, arent worth it unless your already an audiophile. If your running a ~$100 gaming headset, maybe pick up a cheap sound card purely for the headphone amp, but dont get anything special.
Networking adapters would only be necessary if you need to use wireless, or you have a beefy 10Gb/s home network.
For my build, as long as it supports Micro-ATX or larger, its good. Though if you do end up with an ATX case, I would recommend getting an ATX board.

The Titan Black is a highly expensive card. U'll not be getting much for ur extra bucks. manofchalk's build is great. I suggest u go for that. My build is very expensive but it only results in very less performance increase than manofchalk's build.

Yup.

My comment on mobo compatibility is because you mentioned you might go with a different case.
Motherboards have different size form factors (small ITX -> MATX -> ATX -> EATX -> HPTX large), just make sure that whichever your motherboard is, its supported by the case.
What looks appealing is your preference, if you want case recommendations based on aesthetic I need to know what you like first.

Not so much larger, but you see more.
Nothing would need to be added, just screens. Playing at that resolution you might want to throw another graphics card at it if you want to max things out with a good FPS, but for most games a single 780Ti will perform adequately at high-ish settings.

X79 platforms have more PCIe 16x slots than mainstream platforms do, so its possible to run Quad SLI/Crossfire on those. Though multi-GPU scaling beyond two cards degrades pretty badly. If one card is equal to 100% performance, the performance of two cards is 180%, three cards is like 230% and Four is like 260%. As you add more cards your getting less performance each time, so its not that good an idea value wise.

Generally if you mess up an overclock (and you would have to mess it up very badly to fry something), only the component being tinkered with would take any damage.
PSU is fine for overclocking that rig, and the 212 EVO heatsink should be fine for an overclock too ~4.3Ghz on the CPU.

Origin high performance fans just means they fill the fan slots (or replace the stock ones), doubt the fans are any good though.
Onboard audio and networking is them selling the motherboards features again.
AverMedia Live Gamer Portable, that could be very useful if your interested in game streaming or recording.

Both of those cases are pretty good, between the two of them it doesnt matter too much.
Nvidia dont sell graphics cards to the consumer (not directly anyway). They sell reference cards to their board partners (companies like EVGA, Gigabyte, ASUS, etc) who either modify it in some aspect (their own cooler for instance) or just slap a sticker with their name on it and re-sell it. Chances are Origin are receiving reference boards from Nvidia, hence why they arent branded with any board partners names. Keep in mind that a reference cooler like what would be on that card is nowhere as good as the Windforce cooler on the Gigabyte card I recommend.
The brand of the card doesnt matter when it comes to SLI'ing them.

The Titan Black I suppose you could say is the best parts of the 780Ti and the Titan. The Titan has a lot of computing grunt but disabled SMX cores (Gaming) which the 780Ti has enabled, but also is cut down on the CUDA cores that make the Titan a powerful workhorse. The Titan Black is a full GK110 GPU with all the CUDA and SMX cores enabled.

Overclocking yourself costs nothing except the price of cooling it.
Windows 8 is fine in terms of compatibility, more people are annoyed at the [strike]Metro[/strike] Modern UI more than anything else.

The 212 EVO in my build is a heatsink for cooling the CPU, your covered in that aspect unless you want to get into heavy overclocking.
Define "look more appealing", I dont know what you like.
LED lighting you can get, look up the NZXT Hue.
You can buy and install your own capture card if you want.
You should be able to move stuff over with no issue.
As a rule of thumb, 550W for a single GPU, 750W for two and 1000W+ for three of four.
Peripherals are pretty much personal preference, look up ergonomic guides for mice so you can determine which one is best you. Keyboards, I recommend something mechanical. Monitors, check my sig, that will tell you what to look for.

Drivers are what let Windows (or whatever OS) give instructions to the GPU. You can buy games however you want, Steam is just a popular platform. You want to install games to the HDD.

So you want something aggressive looking with a side panel window.
You could check out the Coolermaster HAF series (I have the HAF-X) but its an old series now and lacks a lot of modern features. The Silverstone Raven is an option (and they have a nice rotated mobo). The NZXT Phantom series and the Corsair C70 may also suit. Though in general the case market has shifted toward sleeker looks.

oh, without an optical drive. You can get one if you want, their cheap and theres no reason you cant slap one into the rig.

Gah, sorry for the late reply.

Look at your hand, take note of how your holding the mouse. Then watch this, it will help you figure out which mouse is going to work for you.
https://www.youtube.com/watch?v=luCxbVslSFM
Keyboards aren't so reliant on ergonomics. Get whichever has the features you want, has good reviews and from a respectable brand. I recommend getting a mechanical keyboard (and make sure to pick an appropriate key switch if you do) but whatever works.

A 120hz monitor (by 120hz I mean any monitor that's above 60hz) is going to be good for gaming, they are supposed to feel a lot smoother than a regular 60hz monitor. I cant say from experience if the difference is massive, I'v only had the chance once to sit in front of one (A Benq 120hz, one of the first 120hz on the market) once at a friends place. The other direction you could go is a higher resolution screen, that will also more than likely be IPS so you get the colour advantage as well.

Fans, buy them after the rig is built if it needs them. Fans are one of those things that when your building on paper, it can be easy to sink a lot of unnecessary money into and ultimately they arent needed. Seen a lot of builds here where the OP has sunk ~$50 into good fans when its obvious that money was gouged out of the GPU, and they were completely useless.