Id get the AMD. The P4s are good but run very hot so your system might have alot of fan noise. Ive never heard of a 6700GS. Did you mean 7600GS? If so go for a 7600GT instead. What brand is the power supply? Stick with name brands like Antec, Enermax and Thermaltake. Cheap one can be unstable and even damage your hardware.