well i built my pc about 1 week ago, everything is new, so there arent any dust and my pc has 5 + 1 cpu Fan... XD i have 45- 49°c now ;D
^ since its so new, could be the thermal paste i suspect... sure you placed it on correctly and firmly
For the people who don't know about it, there is a program called Everest that can monitor your temps and other things about your computer.