I recommend Arctic Cooling Freezer 64 Pro. It's not the best, but it does its job very well. It keeps my Athlon64 3000+ (1800 MHz) at 2550 MHz. Idle temp. = 43 C and full load temp. = 59 C. And my chassis is pretty small and crowded.

I use Thermalright Chill Factor paste. 

I keep my Athlon64 3000+ (Venice) 1.8 GHz at 2.55 GHz (8.5x300 MHz) with no voltage modification. I can raise de frequency to 2.7 GHz, but it gives me errors in Prime95 test. I use an Arctic Cooling Freezer64 Pro cooler, but my case is a little small and it doesn't have a place to mount an additional fan to evacuate the warm air.

You didn't mention your GPU type.

Anyway, the temperature is OK. You shouldn't worry about it.