Difference in Core temps

No. You were not worried before using Coretemp and your temps are fine.

Fair enuff..

cheers for the re-assurance, though 10degrees does sound a lot..

If it was new you might be able to RMA it for that reason, but if it has survived that core temperature difference for a couple years, then it will survive for several more years.

Ebay special I'm afraid..

Coretemp was one of the first apps I ran on the processor when installed, and since then I've been reluctant to overly stress the processor (continued benchmarking, or overclocking) without knowing what would happen if the temperature did rise to a critical point..

How do opterons cope with overheating scenarios? Do they reduce the clock speed until life is peachy again, or go up in smoke?

I've heard rumours that it could be fixed by removing the IHS and clamping the heat-sink directly to the chips, however this seems pretty drastic to me (anything involving a knife and a microprocessor

I don't know how an Opteron behaves, but I would presume that it will either slow down or the system will crash.

I sure wouldn't try that solution. The chip is designed to run at 65°C maximum.