I've got coretemp, and it reads low. says 19/9 for the 2 cores at idle. the 2 number get closer together under load, 34/31.
my Bios sees more than 40 (what I set my fan kickup speed at) and hits 60 pretty quick under load (were I set the alarm).
when I set the fan speed kickup at 50 and alarm at 70, it would idle quiet and never alarm under load.
this is a Brisbane core 6000+ on an Abit NFM2 nView (an old 6150 board) with a Zalman 9700 cooler turned up all the way.
I'm inclined not to believe either reading. Its warmer than 9c in my room, probably about 16c (I'm cheap and its cold out).
Abit took forever to make an updated bios to see the correct Brisbane temps, and hasn't done a bios update since (and now never will), so I don't trust the Bios readings either.