Proc: E8400. Quads don't pay for a gamer. US$200
Proc fan: Zalman CNPS9700@US$80. Indulge yourself and buy AS5 thermalpaste for an extra US$6.
Mobo: 780 from nVidia. If you plan to overclock, EVGA or XFX. If not, Asus. US$269 to US$300 (Asus is more expensive)
GPU: GTX260. One card should be enough by now. In a year from now, when price drops, buy another one if you need and go SLI. (US$400)
Memory: 2X2Gb from any known manufacturer. Corsair, OCZ, Patriot. US$110
PSU: I would recomend some extra watts, maybe around 850W. Any major brand (Thermaltake, Corsair) would do. US$230 on 850W Thermaltake's.
Case: Silverstone TJ10. Yes, it's much more expensive than any other case, but it's worth. US$300
HDD: Seagate 7200.11 750Gb. US$130
Drive: DVD burners for US$30. Plus blue ray reader, US$130
With these, you're around US$1,900. If you plan to expend your whole US$2,500 budget, buy another GTX260.
And forget about not upgrading for 5 years. In five years from now, you'll only be able to boot your OS with this system...