2nd Build - High Performance without stupid expense

I hope the title says it all - I built my first a few years ago - around 2012 - and have been quite happy; I got lucky with the i7-2600K, turned out very nice. That said, I'm upgrading for maximum compatibility, and to build a real beast of a machine.

Currently trying to decide between motherboards:
GA-Z170X-Gaming 5 (http://www.newegg.com/Product/Product.aspx?Item=N82E16813128836) and
GA-Z170X-Gaming 6...

2nd Build - High Performance without stupid expense