I was actually thinking of getting a Mac Mini to run my Plex Server. Plex is great, but I find that there is occasional buffering when I play to my ATV. It's because I often turn on subtitles for my shows (so I can keep the volume down and not wake the family), which means that Plex needs to transcode the stream. I have a Synology NAS, but it's not that powerful and can struggle to transcode a stream.
You may find that without the Mac Mini server, your Plex streams may struggle.
What I would like to see if Plex alter their platform slightly and have an option so that when sending video to an item which is high powered (like the ATV4) that it does not transcode at the server end and allow the client to do the transcoding.