Those temps are great! Nice and low even under load. Push the clock higher, till it crashes or your Prime95 times hit 70C.
Then, what is the RPM on the stock cooler? If its just too loud for you, or you want to clock higher, pick out a good after market cooler. It will be FAR quieter. And a bit cooler too.....
212+ is a good starter cooler.....
NOTE: I could hit 4.1Ghz with my E8400 and a monster Zalman cooler. But quiet honestly, a huge cooler on a dual core is overkill. Temps were never my problem with the OC....