when i play gta 4 it runs at about 27-40 fps, and it drops rapidly when im in a gun fight, this being a medium settings. i just wanted to know which should i upgrade for better performance, my geforce gtx 560, or my amd anthlon x4 640. also which ever one i am going to upgrade will either be gtx 560 to gtx 660, or anthlon x4 640 to AMD fx-6300