1st Suggestion - The name of the component is more important than the link .... ideally provide both but if you are only going to do one, the name will save us the Repetitive Stress Injury clicking on all the links.
GFX Card - I wouldn't spend the extra money on the 570. The 900 Mhz 560 is way cheaper and is right on its heels in performance. You can also get away w/ a 750 watt power supply w/ twin 560's.
This is it: the world’s first 2 TB or 2,000 GB hard drive. It is not a high-performance 7,200 RPM drive, but a 5,400 RPM energy-efficient drive .... Western Digital doesn’t talk about its actual spindle speeds and prefers to refer to IntelliPower, which is the marketing name for the balance between spindle speed, transfer rate, and caching algorithms, as part of its effort to design drives with the best balance between performance and power consumption. Insiders still say the speed is 5,400 RPM.
They ain't cheap but I'm finding the 2TB and 3TB Barracuda XT's to be stellar performers. Game load times for the Vertex 3 and off the XT in my son's new box are comparable in my tests.
As to the last build, I like the previously posted one better. As for the GTX 580 for $480 .... I don't think so. Ya 850 watt PSU is a great one but it won't do twin 580's so future SLI there is outta the picture. On the other hand, you can get twin 900 Mhz 560 Ti's for less than a single 580, you can power both w/ a 750 watter and they will toast the single 580.
Guru3D uses the following games in their test suite, COD-MW, Bad Company 2, Dirt 2, Far Cry 2, Metro 2033, Dawn of Discovery, Crysis Warhead. Total fps (summing fps in each game @ 1920 x 1200) for the various options in parenthesis (single card / SL or CF) are tabulated below along with their cost in dollars per frame single card - CF or SLI:
So for $480, you can get a single 580 and get 616 fps. Twin 560 Ti's at the factory set 900 Mhz gets you 862 fps (40% increase in speed) for $40 less. Jumping to twin 580s at $960 gets you 11% more than the twin 560's but at more than 220% of the 560's cost since ya gotta buy a bigger PSU
I'd also add a CPU cooler such as the Mugen 2 or 3