Video card is everything! Though having a good CPU and lots of ram help, but when it comes to gaming most of the work is done by the video card. The textures explosions, mip maps, and all that crazy visual stuff is all put on the video card to do the work.
Now with most games out today a 2 or 3 year old 8800 gt 512 (you can get for $50 now a days, should be all you need (forget the dual video card crap I did that and it did nothing to improve the FPS I just spent money on 2 expensive video cards)
But with Crysis, well truth is the way the game is programed leaves alot to be desired. Its the lighting used to make the texture glow as if you are really outside, its hard on any video card to do, they call that "pixle shading" Pixil shading is also used to make a texture appear 3d even though its just a plain old texture.
2 years ago when I firs got crysis I tried playing with at the time was the best vid card on the market a 9800 gx2 $400 when I bought it, it played it but at low settings. 20 to 30 fps I got frustrated with all the lock ups and errors.
So I wated and now I went out and got a cheap ATI card a 5770 $120 well its a mid level card from ATI, and yea it wont do full settings with crysis but I am playing it with good visials all around and the frame rates are around 75 fps not bad.
So i would say keep you cpu and memory and upgrade the video, the better the card the better crysis will play, besides crysis wars included in the "warhead" game is in 32 bit mode only unless you are playing from the original crysis game and I think it has a 64 bit mode I am not sure.
Oh yea make sure you main board has PCI express slot, you may have 2 but man dont waste your money on 2 video cards I did and it made no difference.