Tight budget desktop for gaming and work

any recommendation would be great, my budget is around 600$-700$ only excluding the monitor..

Are you building because of price, control over part selection, or because you enjoy building ? I ask because it is possible to get more than you have listed right at $700 from such as

http://www.dell.com/content/topics/segtopic.aspx/xps-de...

I have always built my own systems, for all 3 of the reasons I previously listed.

If we want to stick with building, I think you are going too light on the cpu and video card. I'll see what I can find and post a reply with possible alternatives.

the i3 build would be much better but lose the cooler master PSU, they are not the best quality.
Antec EarthWatts Green EA-380D Green 380W $44.99
http://www.newegg.com/Product/Product.aspx?Item=N82E168...

and if you are going to game at all a HD 7770 graphics card is a nice choice for a tight budget.
HIS H777F1G2M Radeon HD 7770 $119.99
http://www.newegg.com/Product/Product.aspx?Item=N82E168...

Ok.....I went ahead and subbed parts according to what you listed, trying to stay with the brands you listed assuming you liked them ( except for PSU ).

I assembled these parts on newegg for $688.92

Intel Core i5-2500 Sandy Bridge 3.3GHz
- http://www.newegg.com/Product/Product.aspx?Item=N82E168...

ASRock B75 PRO3 LGA 1155 Intel B75 HDMI SATA 6Gb/s USB 3.0 ATX Intel Motherboard
- http://www.newegg.com/Product/Product.aspx?Item=N82E168...

Seagate Barracuda 7200.12 ST3500413AS 500GB 7200 RPM 16MB Cache SATA 6.0Gb/s
- http://www.newegg.com/Product/Product.aspx?Item=N82E168...

CORSAIR XMS3 4GB (2 x 2GB) 240-Pin DDR3 SDRAM DDR3 1333
- http://www.newegg.com/Product/Product.aspx?Item=N82E168...

SAMSUNG 22X DVD Burner
- http://www.newegg.com/Product/Product.aspx?Item=N82E168...

COOLER MASTER Elite 430
- http://www.newegg.com/Product/Product.aspx?Item=N82E168...

CORSAIR Builder Series CX500 V2 500W
- http://www.newegg.com/Product/Product.aspx?Item=N82E168...

XFX Double D Black Edition
- http://www.newegg.com/Product/Product.aspx?Item=N82E168...

This gives you a system with a CPU that will keep up with modern times, and last you a good few years. The Mobo supports usb 3.0 and PCIe 3.0 for the latest video cards.

IF you need to cut price, there are cheaper 7770 series video cards to choose from, I just went with the best I saw since it came under the $700 total.

thanks for the advice guys, its really about price right now really on a tight budget lol and probably the selection in our country is somewhat limited so im kinda force to what they really have, I'm from the Philippines by the way.. so the only thing needs to be replaced is the PSU and GPU right? so all other parts are okay? im going with the I3 core built..

yes, please get another PSU!  
btw, as far as a grphics card to run BF3 here is an older article about what entry level card you may consider. the 7770 was not released yet but you can expect better than a 6770 or 550ti . .or there about with it.:
http://www.tomshardware.com/reviews/battlefield-3-graph...

good luck  

Mabuhay thrakazog thanks... thanks guys for lending me with your expertise, thanks for the help im gonna buy tomorrow.. have a great day..

Best answer selected by tukbol7.

for the price of the HD 7770, you can get a 6870
http://www.newegg.com/Product/Product.aspx?Item=N82E168...

look at the performance difference.
http://www.anandtech.com/bench/Product/536?vs=540

Hi just a follow-up to my thread.. I went out and buy earlier today with my specs, but the difference now is my processor, right now it is an INTEL G630 (2.7g), it really saves me money and the store owner said it is no different from performance standpoint on my previous choice which is Intel Core I3-2100 is this true?

The G630 is cheaper, but you take a hit in performance. For standard stuff you probably won't notice a difference, but for more intense things ( like gaming ) it will show a bit more.

Comparison - http://compare-processors.com/intel-pentium-g630-vs-cor...

wow now i know i was trolled by that guy lol, but its okay it saves me money i may just upgrade in coming months.. thanks thrakazog..