With my 8370 I currently have the Xigmatek DK-S1283 which is 13.8c above ambient in frostytech's 125w benchmark. At 1.35v and OC only to 4.2 (lost cores to errors in prime95 at 4.3 and 4.4) I hit 63c max. At 1.4v it was thermally throdling at 70c.
On frostytech's chart the best cooler that fits my case is the Coolermaster Nepton 140XL which is at 7.1c over ambient. That is a 6.7C difference from mine so assuming I bought that could I assume to see temps at 56c at 1.35v and around 64c at 1.4v?
It seems like other people get much lower temps at these voltages with similar coolers to mine. I have reinstalled the cooler to be sure and it seems to be on there correctly with my arctic silver paste. For testing I just set the cpu fan to max and have two 140mm fans blowing out of the case right over the cooler. Do I have a hot chip or something?