Best Program For monitoring Temps + Thermal Paste Question

I am looking for a good accurate CPU temp monitoring program for my Q6600. I am currently using Speed Fan 4.32 but read that it doesnt accurately measure quad core CPUs (+15c correction factor). So I downloaded Speed Fan 4.33 Beta 18, which was to have corrected the issue, but it semms like it too needs the correction factor applied. So I tried Pc Wizard 2007 and it is giving me temps which are 5c hotter than Speed Fan with the correction factor applied (47c load Pc Wizard 2007, 42c load Speed Fan). 5c seems like a big differance between the two programs so I was wondering which program is most accurate, or if there are other programs which are just as accurate? Also, how long does it take freshly applied thermal paste to set in before it finally starts to work its magic?