The latest MED500X supports high definition sound pass-through. It has an updated Realtek chip (1073DD+ chip). From the outside you can identify it by a round(/circular?) blue sticker on the packaging and the back of the unit. So... if you are looking for HD sound...
More details here: http://www.mede8erforum.com/index.php/topic,2517.15.html
More details here: http://www.mede8erforum.com/index.php/topic,2517.15.html
