Many swear by RealTemp. I've used it before and it seems fairly accurate. However, I prefer SpeedFan; force of habit. Regardless of what you use though, you should be getting roughly the same results, which to me suggests that perhaps the early quad cores, just like the core 2 quads do not have the best temp sensors, i.e. my Q9400's cores 3 and 4 tend to "stick" at 37 on idle, but change once they make it past 37, while 1 and 2 do not "stick" and give me fairly constant readings.