Well, I've thrown in the towel and decided that whatever my the cause of heat issue, it seems to primarily point back to the Xigmatek HDT-S1283. However great everybody else thinks HDT is, it's not working for me. I'll go with the flat, thin base on the heatsink from now on. I did notice that BenchmarkReview updated their thermal interface material test to 80 from 33 and included method and enthusiast ratings for the TIMs.

I've gone ahead and ordered a Prolimatech Megahalems with...

OK, I'm all confused now. Temperatures are back near normal again, although I do think a 1C change since updating to the 1303 BIOS revision is strange (core temp = ~44-45C ).

I've changed nothing, but I did notice while I was rummaging around in the BIOS that the VCore is 1.481V. I remember having read that the "stock" voltage for this cpu is 1.35V and it's range is 0.875-1.5V, hmm, . I manually set the voltage starting at 1.2V and raised it in 0.025...