You can buy a new system with a Core i7-900 series CPU. Those sensors work excellent at idle or at full load.

With a 45nm Core 2 CPU, you're screwed. Your sensors actually work better than most Core 2 CPUs and at least now you know their sticking point. These sensors were not designed to report accurate idle temperatures. For that purpose, they're all junk. Some are worse than others but none of them are worth a damn.