i built a celeron D 2.4ghz comp for my parent, everything stock, and there is only one exaust fan. The thing at idle is around 50 degrees c at full load i've seen it hit 65 C.
70C is hot, but in my case i dont care cause it works stable and does not throtle, and it only need to survive like 4 years after that it will be chucked.
By the way is that idle or load temp?
Try chabging the thermal paste and remounting the hsf.