ASUS P5N-D 750i x2 Pci-E
Geforce 9800GTX + [overclocked]
Intel core2 duo e8400 [overclocked > 3.6Ghz]
Corsair DOMINATOR 4Gb (2*2Gb dual channel) [overclocked 1066Mhz]
Cooler master CM 690 Nvidia edition SLI certified
500Gb 7200
600W cooler master PSU
possible 2x 9800GTX + SLI in the future

or:
ASUS P5Q Pro
Radeon Diamond HD4850 / 4870
Intel core2 duo [overclocked > 3.7Ghz]
Corsair DOMINATOR 4Gb (2*2Gb dual channel) [overclocked 1066Mhz]
Cooler master HAF 932
500Gb 7200
600W cooler master PSU
possible 2x 4850 Crossfire in the future, or single 4870 / 4870x2 when the prices drop.

The only thing I'm still uncertain about is whether to go quad-core or not.