Fast computer build in $900?

Are you saying you have that hard drive already or that's what you want? Is it part of the budget?

Case: RAIDMAX Tornado ATX-238WU ATX Mid Tower ($56)

CPU: Intel Core i5-2500K 3.3GHz (3.7GHz Turbo Boost) ($220)

HSF: COOLER MASTER Hyper 212 Plus CPU Cooler ($27)

MB: ASRock P67 PRO3 (B3) LGA 1155 Intel P67 SATA 6Gb/s USB 3.0 ATX ($108)

RAM: CORSAIR Vengeance 8GB (2 x 4GB) 240-Pin DDR3 SDRAM DDR3 1600 ($40)

OS: Microsoft Windows 7 Home Premium SP1 64-bit ($100)

PSU: Antec EarthWatts Green EA-380D 380W 80 PLUS BRONZE ($47)

ODD: LG DVD Burner Black SATA ($18)

SSD: OCZ Synapse Cache 64GB SATA III MLC Internal Solid State Drive ($155)

Total: $771 before $10 mail-in rebate.

The i5-2500k is as good as the i7-2600k for pretty much anything except video encoding, for $100 less [1]. If you overclock, you can get at least a 30% benefit on your CPU. If you don't want to overclock, you can save money by going down to the i5-2500 (exact same non-overclocked speed, $25 less) and dropping the aftermarket cooler.

8GB of RAM should be enough unless you're doing really heavy Photoshop work; if that's the case, you can just get two of the RAM kits above and use them both.

If you want your applications to open up fast and your computer to be really responsive, you should get a solid state drive (SSD). If you're comfortable having two storage disks, a small (~64GB) disk for Windows and your programs, and a larger 500GB+ disk for your movies and pictures and stuff, you should get the Samsung 830. If you're not comfortable messing around with your storage, and want something that you can just plug in during the build, install some software, and have it work on its own, you should get the OCZ Synapse above to complement your storage drive.

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erika,
having found this post of yours it occurred to me that I would ask if you could please estimate how much faster would your your build would be over my current Desktop PC the one that is described in my profile.

I would appreciate your opinion cause I would only embark in putting together a new one once mine becomes too slow or too obsolete compared with new technologies. Mine is over 2 years old.
In my case I also want a fast machine, with zero interest in playing video graphics games. I do lots of calculations, watch TV on my pc via a TV Tuner and Windows Media Center, voice chat over Internet, copy and upload/downloads files to the internet cloud and between my mechanical HDDs.online chat, email, web surfing and feeding a couple of HD Monitors.
I also own an Intel 320 Series SSD, which is only Sata 2 (capable of 3Gb/ps speeds)

I would appreciate your comments.

Thank you kindly

Anandtech has a great tool for quickly comparing CPU benchmarks here.

What exactly do you mean by "do a lot of calculations?" Everything else you've mentioned is light work and the Q9550 should be more than sufficient.

It sounds like you already have a pretty good computer. In my opinion, the Core 2 Quads are still perfectly viable processors. If you're having trouble feeding the multi-monitor setup, you may want to get a budget modern graphics card, but aside from that what you have sounds like it should fit your usage just fine.

I think all of the Intel 320s are SATA II. The 510s are SATA III and will run faster on a new motherboard, but I think a lot of the benefit of SSDs is from the lower latency resulting in a more responsive system, and you already have that. The drive will perform up to 60% faster when plugged into a SATA III port, which sounds like a lot, but it won't be the huge difference it was when you first moved to an SSD from a HDD.

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Spreadsheets are the "lots of calculations" I mentioned on my previous post, but it sounds that you think the Quad I have is good enough.
My SSD is rather new and I think I havent yet fine tuned it to be as fast as it can be. My best CrystalDisk benchmark readings until now are the following:
Sequential Read 246.0 Mb/s Write 171.2
512K Read 128.9 Write 170.8
4K Read 19.85 Write 38.87
4K QD 32 Read 21.05 Write 55.21

I have not done tinkering yet. I think I need to look for Intel firmware and install it. And also use the Intel SSD Toolbox to do something with it. Are you familiar with the process?
Also, do you know how to refresh the SSD daily to keep it running at the original speed?

Thank you again

I have an OCZ SSD so I'm familiar with the tweaks (here's a guide, or you can just use the tool for the same effect with 1% of the effort  ), but not with Intel's firmware or other tools.

If you have Windows 7, trim should be automatic. You don't need to perform any kind of daily maintenance. And your speeds look fine to me. I wouldn't sweat it. Update the firmware and Intel RST if you want, and then forget about it. It's going to run at the speed it runs. All constant benching is going to do is wear out the drive faster and accumulate a lot of garbage, making your drive slower until trim has a chance to clean it up.

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Thank you very much again.
Cheers.