If you game at resolutions 1920x1200+, newer processors do next to nothing for you.
http://www.insidehw.com/Reviews/CPU/...ad/Page-3.html
In the above example, Crysis Warhead gains 0.9FPS when switching from a Core2Quad to i7 with all other hardware remaining identical.
TLDR: At modern resolutions, i7 does nothing for gaming and you can save a lot of money by building around older Core2 technology, and instead put that money into a top-of-the-line GPU which will net you better performance. 2x 5970 Quad Crossfire would be the best available setup you could get until Fermi.