Best bet is to use the PI as a client, plex server is dependent on FFMPEG transcoding which seems to be best served by a high IPC cpu e.g. Intel Core w/ quick sync support - my plex server is setup on an i5-550, does ok but struggles on the 2nd stream. Sandy Bridge and later series have quick sync support, will have much better transcoding performance over mine and should support 2+ streams much better.