I currently have a Phenom II x4 945 & a Sapphire HD7770 GHz Edition
I can run the game on High (Laptop) fine and the game runs on Max albeit a little choppy.

I'd like to upgrade to the HD7950 to hopefully get 60fps on Max. I'm worried my CPU will bottleneck this GPU and I'm wondering if I'd get a better return out of upgrading the Phenom II to an i5 4670. Currently, I can only afford one as neither are cheap on a budget.

I'd prefer not to do any OCing.