I will second on plex vote.
If you are not doing any of the FANCY stuff, like TV card recording, etc with it.. which you would need something more XMBC based, etc.. and its just for playback... Plex is the simplest and works well.
(though, this will require the PLEX media server software to be installed.. which can be installed on SOME brand NAS's... but could always install on something else, and have it just map drives to the NAS)
The SERVER software, has scrappers which go out and collect the Movie, TV, etc info, and keep in its own database. As long as it finds the right match for the movie, I have never had it not have/get stuff.
From there on playback PC, install Plex Home Theatre. XMBC like nice fluid interface.
Rogers Ignite Xi6, LG 47LV5400 LED TV, Yamaha