There are some 64bit/32bit pci-x cards around. No video card goes in the pci-x (64bit pci ) slot. It's either agp or pci-e.. If I were you I'd get a A64/Opteron setup that supported pci-e,
because that's the future of video cards. Also w/ a mobo like the one I linked to , you'd be able to get a 6800gt now, and then later if you wanted , you could add a 2nd 6800gt for a sli configuration.
As for as scsi, simply its the best .. The 15k drives are so fast at everything, I only use the raptors for video editing, and use the 1st 15k for multi os's , 2nd for programs, and the 3rd for scratch space.
Again most users won't have a systems close to what your looking at, but considering you have the money why not get the best...
Regards,
Jose