You've got plenty of power there, my system (see sig.) is able to run it ~30fps for most of the game with the dx9 tweak, I put everything on Very High except shadows on Medium @ 1680 x 1050. It was fun, beat it I now have no reason to play it. Except I just built a system last night for a friend and I was able to get 30-45 fps on DX10 with ALL settings on VERY HIGH, here's the specs:
E8400 @ 3.0Ghz (stock)
Abit P35-E
Crucial Ballistix 2 x4 GB DDR2 6400 @ 800Mhz
EVGA 9800 GX2 <---- Can't justify the $$$ for my own system...
I haven't delivered it to my friend yet but I think he will be very pleased...
**Edit** I don't recommend building a pc just for Crysis as the game was disappointing in the end. But the parts you plan on getting will be solid for any of the other great games out there. Just an FYI the system I built for my friend cost him $1450 shipped, parts from various places on the net. Also, was built from ground up including case drives psu...