If you want to have a fully functional computer system dedicated to your tv/entertainment center, check this out:
these cpu's are really slim and can easily fit behind a wall mounted tv
these specific models are fanless, and basically silent (especially with solid state drive(s))
wifi capability
hdmi out
the best resolution possible
but let's say you have an older plasma tv on a low profile mount,
this one is designed to be in extreme environments
(you may have to sacrifice a tiny bit of profile "lowness") <---- it's in the dictionary.....I checked