Ran a CPU stability test and although I didn't do it for too long I think it is stable. On my motherboard there was an option to overclock to 10% instead of changing things that I don't know much about I just did this and every thing looks fine.
After playing CoD4 demo again, the game does run at 2560 x 1600 around 30fps, but lowers to around 24 in intense action which I think is pretty good. Everything on max.