X99 with an I7 6850k will get you true 40x lanes and 16 x3.0 support.
I think that's the cheapest true entry point for stuff you can still buy new.
It's the route I took in the last month.
Z270's method isn't the same. Those CPUs only support 20 lanes and coffee lake isn't coming out on 1151.
My understanding is coffee lake won't work with existing z170 and z270 boards.Coffee Lake is 1151, there is no word on its lane count as of yet but likely same as kaby/sky.
regardless of all this talk, Multi GPU is dying and still isn't usually limited by 2x 8x PCI-E 3.0 in the majority of metrics.
PLX chip fix to expand lanes isn't really expanding them its just sharing lanes but hey if you feel like seeing x16 on both GPUs for the sake of it sure buy the WS board with a PLX, an Asus Maximus IX Apex board for 100 less with better DDR4 capability will kick it around like its nothing in benchmarks and top scores any day of the week because CPU and its Ram are the bottlneck at the top end of performance not gpus and PCI-E lanes.