Hi andy, thanks very much for your reply.
I like monitoring my system but if I had such unrealistic values like you, hm .. that's not nice.
There doesn't seem to be anything one can do, to re-calibrate I guess. Would have thought to get accurate readings from an external thermometer and enter the values into BIOS.
Computers still don't seem to be
that smart, hm.
Regarding cores affecting each other, well ... Aida64 shows the values for each core of my Q9550 here:

... but I think one single value (Utilization & Temperature) in average for all four of them should be fine.
By the way, I have ordered the Mini iTX board Intel DH67CF B3 which apparently does a good job in staying cool .. ►

I like the following features ...
• Extensive option for configuring and adjusting rotation speed of the two 4-pin fans:
-» Specify parameters describing the dependence of fan rotation speed on the teperature
-» Determin which temperature should affect the fan rotation speed
• Four (!) thermal diodes » CPU, RAM, CPU voltage regulator and chipset
• Allows under- and overclocking the Intel HD Graphics core but not (!) the processor core voltage
I just don't understand why Intel does not support undervolting.
It's not like the H67 chipset can't do it because the Gigabyte GA-H67N can do it.
It allows the CPU Vcore to be changed between 0.750V and 1.795V in 0.005V increments.
Was thinking for a few weeks between these two boards but cause many seem to have had serious issue with the VGA driver, I've gone back to Intel.
Some of the Intel boards however, have problems with dual monitor configuration. If that happens to me, I'm gonne give the Gigabyte a chance.
It was clear for me that I won't use a descrete graphics card, so I do like the idea of the GPU being part of the CPU.
What I still don't feel confident about is the decision between i3 2100 and i5 2500K. At the end I have gone with the Demon, but hm ...