Sorry but you don't know what you're talking about. Every individual card will have a different upper limit to the next. Maxwell doesn't scale well with temperature like Kepler did, and seeing as you're limited to 87mv it makes no odds.
I have three on water and none of them do more than 1570. where as 1580 "easily" as you describe it is all very nice, it's nothing to do with anything you've done. It's all down to the silicon. Plus as already said a lot of benchmarks will be bouncing off the power limit regardless.
Edited by Silent Scone - 10/18/14 at 6:34am