Considering the Viewport performance in Rhino 5 Rhino Viewport FPS topic just a faster GPU won’t improve Viewportperformance. Hence, I am planning to upgrade my system. A friend of mine (also productdesigner) requested my help to configure his machine. something like 1700x 32gb (2x16gb ddr4 3200). Myself I am using a RX 480 which is used better in Rhino WIP.
You will benefit from 8C/16T if you render from time to time. Mostly the crucial last days before a presentation you will be happy about more speed. Dropping the time (e.g. 1h with fx 8350) to only 20 mins for each picture 