The motherboard you chose is specifically designed for multiple GPU gaming. I see no reason to buy it otherwise, as the rest of the features are just average. It's too large a percentage of your total budget.
Will you overclock?
What monitor resolution and how many?
Is this an office environment or home? Is there a network with a router?
Based on what you plan to use your build for, it seems like you would benefit from using a Z68 motherboard, 60GB SSD and 1TB Samsung SpinPoint F3 HDD and make use of the SSD Caching/Intel SRT. (You could add another SpinPoint and run RAID0 if you wanted more than 1TB storage space).
i5-2500k is a solid recommended CPU
6950/GTX 560Ti is probably your best GPU choice on your budget.
8GB of RAM i would expect to be enough, you can always add another 8GB if you really have to.
OS - Windows 7 64-Bit, Home or Professional.
@ Proximon : So I bought the hardware you suggested and assembled the computer. The computer is running nicely, but I have a few corrections:
The RAM module you suggested contains 4 x 4GB but there are only 2 slots on the motherboard so I am only able to install 8GB...
The CPU cooler is HUGE and it took me some time to install it. I accidently installed it vertically instead of horizontally which resulted in no room for the graphics card. So I had to uninstall it and rotate it. My fault but I just wanted to share this.
I installed Windows 7 Home on the PC. By default the processor was running at 1600Mhz, so I clocked it up to 3600Mhz using the software utility that comes with the motherboard.
Only issue I see is the mouse "stuttering"..When I move the mouse pointer from one side of the screen to the other side, the mouse pointer will make sudden halts and then move again (even though I am moving the mouse). It is really annoying. I think it might be related to the quality of the mouse (going to buy a better one). When the mouse pointer "stutters" I hear the audio being distorted as well. So then again..it might not be the mouse...Any tips on this one?
The fans are really noisy so I guess I have to get used to that.
I'm so sorry about the RAM. That's a huge mistake and one I normally don't make. You probably need 16GB also? Normally I don't expect a build I present to just be jumped on quite so fast.
The processor was probably just throttled down. It has idle mode and turbo mode, and stages in-between. The way to test it would be to use Real Temp, CPU-Z, and Prime95 together. Then you will see the full picture. Ideally you would have a turbo mode around 4.4Ghz, which is still a conservative overclock. But of course all CPUs vary.
With new hardware I am seeing that Win 7 sometimes misses USB drivers. It doesn't get everything installed and doesn't tell you about it. For that reason, on new hardware released after Win 7, I normally use the CD that came with the board and make sure I have all the board drivers.
Start menu-computer-r.click and properties to get to device manager. Under USB controllers you should have 10 or more items. Less than that points to this problem.
A defective mouse or USB port could cause this as well.
Or control the voltage to the fans you have so that they don't run at full speed.
Again, sorry about the RAM. That's the worst mistake in about two years... Last one was a motherboard with heatsinks so high the buyer couldn't get his fingers under the cooler to install it, on an AMD build.