said by not quite right:if all you're worried about is running plex, why not get a roku for $79?
While a Roku does a "good enough" job with Plex (I've set up a Roku 2 XS for a friend to access my content remotely), it hardly compares to a mini or similar HTPC running a full Plex client... (in the case of the Roku, you had better have a box with a bit of horsepower to install the Plex Media Server on it to help with transcoding to the Roku...)