CPU temps are different from CPU core temps, and idle is much less of a concern than "under load".
Download and run OCCT and look for something along these lines (2600k, HT enabled):
Stock 51,53, 53, 51
4.0 Ghz 52, 54, 55, 52
4.2 GHz 54, 56, 57, 55
4.4 Ghz 56, 60, 60, 67
4.6 Ghz 62, 66, 68, 65
4.8 Ghz 67, 71, 73, 70
Disabling HT will drop ya temps as much a 7C at the 4.8 Ghz point
http://www.ocbase.com/