I have tried a few of those programs, it seems that they are pretty consistent in their readings, so really I can stick to either SpeedFan or RealTemp. Although what's weird is that both these programs report lower temperatures than when I go into the BIOS.
Just now, after my system has been running for a while, when I reboot and go into the BIOS (Gigabyte board), it reports average idle temps of each core being 36 C. And then after window loads and RealTemp loads, the temps for each core reported there is significantly lower - around 29C.
SpeedFan also seems useless in regulating the CPU fan speed - it's spinning near 1049 RPM no matter what.
Maybe my mobo has a setting that's not letting SpeedFan do its job?