Hello. Hopefully a easy question. I have dug thru the forums and did not see the answer for this so here it goes. For hardware transcoding, I know that the plex requirements are for a CPU with Quicksync support and there is a side note about being able to use your GPU “when Intel Quick Sync Video becomes unavailable” but does that mean that if you have a CPU that does NOT support Quick Sync but a good GPU that would be able to do the transcoding that it will not because the CPU does not support it?
As far as I know, the GPU should be used anyway, but know that discrete GPUs aren’t officially supported right now. Most recent ones will work under Windows or macOS, though.
I have a Gtx 1080 and an I7 5960x. I been able to use hardware transcoding up to 5 concurrent streams with no issues. But like KarlDag said, most recent ones will work. Not sure of older models.
Let me throw in a bit more information. My Plex server is a Dell T310 (8 bay) so it has redundant drives, a real raid controller, redundant power, etc. A real server (32GB RAM, Xeon X3440). I know that the processor does not support QuickSync Video but the processor will handle all but transcoding so far up to 4k, thats where it is getting its butt handed to it. Trying to figure out if I throw a Maxwell based NVidia card in like a GTX 950 if that will boost the transcoding (or any AMD card that would fit the bill but I dont know much about AMD). This is not a gaming rig so the cheaper the card I can find the better. It only ever displays a desktop. 
@gvbhunt said:
Let me throw in a bit more information. My Plex server is a Dell T310 (8 bay) so it has redundant drives, a real raid controller, redundant power, etc. A real server (32GB RAM, Xeon X3440). I know that the processor does not support QuickSync Video but the processor will handle all but transcoding so far up to 4k, thats where it is getting its butt handed to it. Trying to figure out if I throw a Maxwell based NVidia card in like a GTX 950 if that will boost the transcoding (or any AMD card that would fit the bill but I dont know much about AMD). This is not a gaming rig so the cheaper the card I can find the better. It only ever displays a desktop.
If you want to be future proof with 4k support and HEVC and HDR and the most possible stuff supported, I’d go with the most recent Gen. A GTX 1050 or even 1030 would probably be better. Same for AMD, is go with a Rx460 or better, personally.
Edit sorry the 1030 doesn’t do nvenc. So 1050.
So I ended up going with a budget GT710 in the Plex Server. Does an amazing job offloading the transcoding of everything but HEVC (thats ok, I have no 4k TV’s anyway). CPU usage dropped from around 60% to close to 15%.
