For simple gaming and streaming i would recommend a 5820k Haswell-E / 6800K Broadwell-E. It's cheap , 6 cores but only 28 lanes
5930K / 6850K also 6 cores on the other hand , got 40 lanes and would not have a problem with 4x graphic cards or 2x graphic cards and other Pci components all togheter.
5960X 8cores / 6950X 10 cores is the ultimate choice, but with a cost! and not really for gaming and streaming. it's just overkill 😛
Yes after updating the rampage V Bios to atleast 3008 , it will support Broadwell-E processors , but if you don't want to spend like €30 more for the Broadwell-E 6800k , over the 5820k Haswell-E , go for the 5820k.