To run Crysis at a reasonable framerate you're talking about 2x 8800GTs or 8800GTXs in SLI for high
Crysis runs at 25 to 35 FPS on my rig on high settings in XP with a single 8800 ultra, x6800, 2gigs, and hardware raid, if I apply the dx10 tweaks it drops to 25 to 30 fps and is some what slower in both cases when theres lots of action but its very playable and looks absolutely brilliant.
As for Vista it aint ready for prime time so DX10 aint a option IMO but is this Crytek's Fault?
Just like many games before it Crysis is ahead of its time and it will be awhile before hardware that the masses can afford catches up, but as I said before PC gaming has always been expensive if you want the latest hardware.