the 4670 isn't a very strong card for something like crysis. i'm really surprised that it would pull Crysis on max settings.
Anyhow, you can probably bump C2 ingame settings to medium, 720 resolution. If you're not getting good framerates, try some of these console commands:
r_colorgrading = 0
e_shadows = 0
It's not gonna be as purty, but you'll get better framerates