If ur motherboard temps are OK, then i think u need to buy a good quality CPU cooling fan instead of using the stock cooling fan. Also, use a good thermal compound like Arctic Silver 5.
Even i am facing a problem with my latest Core 2 Duo system. The CPU fan runs only at 1100 rpm. The idle temp is around 40 but when i run games it reaches 55 because the fan is running only at 1100 rpm. Checked Intel's site: they said that the fan speed will increase only when the CPU temp reaches 75 degrees.
Contacted Intel support center, they gave me a mail in which it was clearly written that the CPU temps should not increase 70 degrees whereas on the Intel's site it was written that the fan speed will increase only when processor temp reaches 75 degrees i.e. when the processor has already fried!!!