What is the best UE4 PC setup? (Mainly CPU) And why?

well I just got test VIVE™ | VIVE Ready Computers and my gtx 960 is bottleneck. Now I want to do steam test to see SteamVR Performance Test on Steam is it going anywere. I am thinking of changing just motherboard then what about memory, cpu… well one leads to another thing. But If I change GPU and need SSD I will have to buy new one.