One of the things that struck me is only one of the Gigabyte boards supports M.2 Sata but the builders chose not to use it. Maybe a budget constraint but $1500 is a fair amount of money. They seem to have op[ted for a higher end GPU vs. overall system speed.
Fractal Design R5 | Asus Z170 Pro | Intel i5 6600k | 16 GB G.Skill Ripjaws DDR4 2133 | Seasonic 650w PSU | eVGA GTX 550 TI | Samsung 960 M2 500 GB | Samsung 850 EVO 500 GB | ASUS Burner | Windows 7 64-bit