If you're for a simple, cheap fix: replace your fans with some higher CFM fans, maybe in the 100cfm area and get a fan controller. Make sure you have enough molex connectors off your PS for fans and the controller itself. You probably just need more air to push around, and keep the case enclosed. I've got six 120cfm fans (2 intake from below, 1 intake on the side, and 3 exhaust up top) and they push around a ton of air. Be weary of increased noise though.
If you want a slightly better fix, invest in a better tower with better breath-ability and more fan placement. If you want even better, go water cooled.