I built one of the dual E5-2570 PCs, put in a GTX 1080 and all latest games run very good on maximum graphics settings.
I get the same results as what I see in other tests with GTX 1080 and 6700K. So I can't confirm that there would be any real performance impact on games with such a setup... Even if I get lower results, it is marginal and way over 60FPS (2560 resolution)