Well, I've never owned a Core architecture processor so the whole "core1, core2, etc." readings look a bit alien to me. I'll tell you what I know, though:
When I replaced the Intel heatsink with a Zalman my CPU temp dropped about 10 degrees C.
Pentium D processors are supposed to run hot. While SpeedFan is reporting 18C for me, PCWizard is reporting 32C. That's not proof that PCWizard is accurate, but it's proof that in my case, SpeedFan is inaccurate. SpeedFan also says my northbridge is at 127C.
Have you checked the temps in your bios? Those should be accurate.