The WD1002FAEX that you are looking at has similar performance to the Spinpoint F3 and 7200.12. All of those drives have 500 GB platters (the WD1001FALS, the older Caviar Black drive does not), so they are very similar from a performance standpoint.
However, the WD1002FAEX doesn't approach using 6 Gb/s (no current mechanical drives do), so the added expense (about $30, I believe) is unnecessary.
yes the vapor x is cooler and makes less noise. Ir's also stock clocked higher( I think maybe only with the toxic). Its better than the stock but more expensive obviously. The best is buying a normal 5870 and sticking a high quility gpu heatsink on it. And PLEASEEEEEEEE people stop this hype about making WD go bankrupt by trying to convince people caviar blacks are slow which they aren't they are faster in some ways and slower in others than the f3 or 12.7200.
GFX Cards - Big difference in card performance on whether or not you're looking for DX 10 or DX11 performance. If you'll be playing mostly older DX10 games, then the ATI cards have the advantage....with DX11, advantage nVidia.
Here's the price / performance numbers in dollars per frame (DX11, 1920 x1200 , hi settings). The 5850 and 470 are almost identical, differing by just 4 cents, and the 470 takes 8 outta 9 DX11 benchies. The 480 takes 10/10 DX11 hi settings benchies and has a 6% better price / performance ratio.
ATI 5850 - 9.04 dollars per frame (fps)
nVidia 470 - 9.08
nVidi 480 - 10.01
ATI 5870 - 10.59
ATI 5970 - 11.93
Again, the 4xx series wins big on the DX11 stuff but the 5xxx series wins many of the Dx9/10 benches.
Hard Drives - There is no best HD .... what you can pick is the HD which performs best in your most used applications. Check out the performance charts and pick whatever 500 GB per platter drive performs best under your usage patterns. The 2 TB WD Black and XT from Seagate are good choice but at smaller capacities, you are limited to the Seagate 7200.12 or the Spinpoint F3. The 7200.12 excels in gaming, multimedia and pictures whereas the F3 wins at music and movie maker. See the comparisons here (copy past link in manually, link won't work in forum):