Hello Alll.I am thinking about upgrading my old 9800gtx.At the moment i am having core 2 duo e6600 at 3.7Ghz with Asus rampage formula x48 and 4gb of ram.PSU is 500W.I am confused because i wanna upgrade the gpu but dont know which one will be the best choice because of the cpu. I am thinking about 6850,7770,550ti or 650ti.