Okay, your CPU is more than fine for this game.
So, what AA setting have you chosen ? TXAA is very intensive, if you wish a smooth 60fps FXAA (high setting) is recommended.
There's basically normal, high, and very high for every graphics setting. Right now I have everything set to normal. As a heads up, switching AA between normal and very high seems to make no difference at all. I will say though, I saw the 360 version of this game at my friend's house, and even on all normal, it looks leagues better