I have a 6-core i7-5820K CPU that's a bit OC'd as well as an nVidia 980 Ti but 4K video is a bit of a struggle with it. The idea that you could have too much power is nonsense though you do have to have the money for it. My nearly two year old editing PC, which I built from scratch, doesn't handle h.265 very well but the newer CPU's and GPU's appear to be able to work with it natively so even a more modest system using new parts should be a lot better when doing h.265. I suspect that in another year or so even mainstream PC's will do 4K video editing pretty well but then people will be doing 6K and 8K -- it never ends!
Let's not talk about storage!
Brian