Plex client - A client device (eg. Amazon Fire TV, Roku devices, etc.) with Plex app that plays the media from your Plex server. [Read: 10 Best Plex client devices: Pre-built and DIY options] In addition, you will need locally stored content on a media server for Plex to catalog.
As far as the CPU goes, this particular server only supports dual CPU, since I plan to run Plex on this box it seemed reasonable to get a beefy CPU for it, and the Xeon E5-2690 v2 3.0 GHz was the beefiest that this seller is currently offering. They full line of CPUs they offer is: * Xeon E5-2630 v2 2.6GHz * Xeon E5-2650 v2 2.6GHz [+$100]