Have yo tried adjustin your power settings up to maximum perfomance? If you still have low fps, then I suggest buying a new psu that must have atleast 600W.
Since you've bought it already, I prefer keep them. Yes they say it's waste when it comes to gaming purposes but still, if you gonna something else using other programs and gaming at the same time, it would be better to have 16gb just in case.
Try resetting your bios. If your not sure how to trouble shoot, look here:
pcsupport.about.com/od/fixtheproblem/tp/clearcmos.htm
There are 3 easy steps you can to reset them
Have you check the inside of your computer to see it's dusty. If so, clean them thoroughly with compressed air cans. Dusts are usually the culprit for over heating and thus, causing the fans in need spin more quickly.