Speedfan should be fairly accurate if it's set up right. It's hard to say where all your readings are coming from. MBM5 readings are way off on my board compared to Speedfan. I get temp readings from a sensor that isn't even there. If you are running a Prescott you should be 10C hotter than a Northwood. Speedfan is the recommended program for the MSI P4 boards and everyone on the MSI Forum says it's the most accurate. It ought to be fine with the ABIT boards too.
"I am become death, the destroyer of worlds. Now, let's eat!