It may have already been said but increasing your PLL and IMC voltages seem to have an effect on performance. Give it a go maybe?

Also, thanks for the tests. I'd be interested to see the 920 bumped up in vcore to match the 860 (even if it's not required). This way we would have an absolute apples to apples comparison... Well as close as possible anyway. My suspect is that the 860 would still be a little faster and more power efficient. It is a newer design, after all so we can pretty much expect that.

Great work here, folks!