You can do soooo much with a $1000 PC.
Rig #1:
CPU - E8400 / E5200 (Depending on budget)
P35 / P45 Chipset Motherboard (ie. P5K - Q)
4 GBs of Ram (DDR2/3 Depending on motherboard)
GPU- 4850 x 2 (or 2x 4850)/ 4870 / 4830 (or 2x 4830)
depending on preference. (P35s (ie. P5K support Crossfire)
(ATi has considerably better graphics cards @ price/performance ratios in current series)
\\ PSU - Considerably good brand PSU (500W as a guide line minimal)
Case - Blah blah blah \\ (ignore)
If you actually want future proof, Core i7s. With the motherboard and a 920 for example, the cost will be around $700. (Depending on where you live). Throw in DDR3 ram, around $200. Throw in a HD4850, goes another $150. A tad over $1000. Again, this is for future proof.
BTW - Dual Cores are still probably better gamers. Quad Cores... ehhh, not right now. If you are doing overclocks, the E5200 with moderate cooling will get (depending on batch) 4 Ghz, even more (45 nm die).
(no point really of getting a Q9300. Might as well get a E5200 or E8xxx and overclock it. You'll save money where you can save elsewhere. Add a 10k Raptor, or// SSD HD. These will further enhance your PC performance. If not, save money here and there, and throw in another HD4870, or even a HD4850 for that matter.
My E2180 is at 3.2 ghz (pumping @ 1.5vCore).
Hope this helps... =DDD