You will probably be fine with a 9800 at that resolution. Possibly not powerfull enough for max quality settings as crysis is a pig for resources. (I get occasional stutter on my 4870 with everything turned up high but thats running at 1680x1050) The rest of the rig is fine too. I would suggest 4gb ram (especially as using vista, and its cheap to buy 4gb now anyways )and something like a 4870 if you intend to play on higher resolutions
I don't think that is correct on RAM and VRAM duplications, but I'm open to persuasion
Crysis takes a lot of RAM though - 3gb seems to be a minimum to reduce hard drive access which shows up as stutting as objects are loaded - thereby affecting the frame rate while the gfx card waits for data to throw around the screen.