Ok, there's your problem right there. Anti-aliasing takes away the jagged lines in 3d games, but it's a big performance hit to the graphics card. And Crysis is so graphics intensive already, that in fact, I don't think I've ever heard about anybody playing Crysis with AA on yet. Your processor is fine and you won't see incredible gains in Crysis by going to Quad.

So turn off Anti-aliasing and you will be able to play Crysis much better.