I'm running Plex Server on a powerfull system (Core i7 4770K-4.5GHz, 16 GB Ram, 54TB Storage, GTX770 graphic card) but when transcoding it's limited to 4-5 clients depending on te source to transcode.
To convert ISO images or TS files I'm using DVDfab with CUDA support, conversion speed of the system around 150 frames per second with CUDA support on, without CUDA support around 65 frames per second, a big difference.
IS CUDA support a option for PLEX??
search -> https://forums.plex.tv/topic/65319-gpu-and-better-multithread-support-for-transcoding/?hl=gpu
And another more recent/relevant thread:
https://forums.plex.tv/topic/117318-cuda-transcoding-support/?hl=cuda
EDIT:
I should point out that if you don't mind a lower quality transcode (only noticeable for bandwidth restricted/remote transcodes), you can select "Prefer Higher Speed Encoding" in in Settings->Server->Transcoder on your Plex Media Server.
Early 2021 clean-up: duplicate/implemented
