Actually, it's a very valid question...as using mobo software temps, or jsut plain bios cpu temps, while accurate in some context, may not show the true benefits due to coarser granularity. And looking at my post, I was obviously to busy thinking about your question to even use proper grammar!
Then, there cpus like mine...DTS reports a minimum 36c temp...with my current cooler, load on stock settings is a mere 38c...almost impossible! So how do I compare idle temps? As teh normal cpu temp sensor DOES read below 36c, it's the only way to measure idle temps...