If you can't trust your BIOS, who do you trust? Wait. Don't answer that. I have a p35c-ds3r. They say the DDR voltages start at 1.8V, but with some RAM it's 2.0V. At least now with the F5 bios, they list the actual voltages in the PC Health section.
The problem is that you can't access the... Nevermind.
Correct me if I'm wrong, but i'm pretty sure Temp reporting programs access the exact same MB sensors as your bios does in order to read temperatures. So, if bios temps are incorrect then is a good bet the temp programs reading would also be fubared.
So, if you think you are getting incorrect temperatures in your bios, I guess you could always give one of these a try: