Yeah gfx card should be Nvidia 8800 GT (SuperSuperclocked if you've got spare money

)
I'd take a hydrocooled quadcore.
This is what my friend has, his pc is current Dutch best (don't know if parts become available faster overthere)
Processor: Intel(R) Core(TM)2 Quad CPU @ 2.66GHz (4 CPUs), ~2.7GHz
Memory: 4 x OCZ reaper pc8500 CL5 1gb
Hard Drive: 2x Seagate Barracuda 7200.10 320gb RAID0
Video Card: NVIDIA GeForce 8800 GTX aquatank
Monitor: SyncMaster 226BW,SyncMaster Magic CX226BW(Digital)
Sound Card: SoundMAX Integrated Digital HD Audio
(also see xfire.com/profile/martijnkolen)