In order to easily handle Crisis you would need 3x GeForce 8800 superclocked cards running in triple SLI just to get a good rate at high settings, let alone super high...
piggybacking on that...some dude made a custom screamin' machine with that, and other freakin' amazing parts
this thing was a monster right? well on all high he could stil only get 30 fps
which is saying somthign because that game is both fun and incredably demanding of your computer
btw you cant have hundreds of gigs of ram like psp said ^
thats not been done (yet)
i have 4.. but xp only sees 3, but i can still run it on 2 low, the rest med/high settings (mix n' match)
but if you wanna do great things get an 8800, good processor, mobo, good ram, etc.
good luck though
oh and crysis is spelled Crysis, not Crisis (made by crytek, uses cry2 engine, crysis)