so what kind of computer can handle h.265? What's the minimum requirement?
Most any decent desktop PC with a supported GPU will do OK though a lesser PC may need to use proxies to be workable. A higher end PC of the last couple years with a good GPU should be able to work H.265 or H.264 without using proxies though you may want to use reduced resolution settings for edit playback. In PP in both the 'source' and 'program' window there's a drop down box just left of the wrench icon a the bottom right of the screen that will either say 'full', '1/2', '1/4', '1/8' or '1/16' -- this sets the resolution during playback while editing and lowering it can smooth the performance. It's a bit like using proxies without using proxies and you can change the setting whenever you wish without effecting the rendered quality or needing to mess with proxy workflow.
So, any decent desktop box of the last couple years with a decent GPU should permit 4K editing with H.265 or H.264 though changing the playback resolution as I describe may be helpful in making the task quicker.
Finally, although I mention the GPU you do not normally need a high end GPU unless you do a LOT of effects -- for most things the component that most determines performance will be the CPU so if you're thinking of buying or building a PC for video editing budget more for the CPU and just get a good GPU. When I render I watch the CPU and GPU temps and find that for most things the CPU goes to max temp while the GPU typically only goes up about a third of the way to max. I do have a high end 980Ti GPU but I also have a good i7-5820K CPU -- both over clocked modestly.
Brian