Weird indeed, but be advised that the push pins might not always fasten all the way, this happened to me when I built another Core 2 system, one of the 4 pins was only partially secured.
If you run the CPU @ stock, you should get somewhere between 32-38C @ idle using the Stock HSF (without C1E or Speedstep enabled that is). And this is from the 3-4 systems I built using Q6600's with stock HSF. All of them used the TIM that came with the stock HSF. Also your stock Vcore is lower than mine was, so again very strange.
Sometimes the TIM takes time to completely settle, so you might see @ 1-3C difference in a couple of days or weeks, but not enough to warrant such a huge difference...