Have you tried CPU-Z to check the multiplier and frequency?
us your pc set to balanced or power saver in control panel? if so try changing it to high performance
I use Core Temp 0.99.8 and Real Temp 3.65.
Both report my 2600K correctly.
RTJ, you are worrying about nothing here matey, just enjoy it and wait for the updated coretemp/realtemp to arrive. the temps recorded by those programs are still correct regardless. Your idle temp seems absolutely fine to me.