I have a Buffalo Linkstation Live 2tb drive (110 a few months ago) and a WD TV Live (~80 a couple of years ago) HD media player hooked up to the AV system with HDMI.
The Linkstation has a DNLA media server in it, or the WD TV can read the folder structure on it. WD TV can play basically anything - best of the dedicated boxes I've found (I'll maybe not be able to play one 1 of 20 downloads).
The NAS drive also has uTorrent built in and remote access from the internet, plus you can hook up another hard drive to it with USB once it fills up... or a printer.

All that stuff works really well for me - can download whole Blu Rays and get all the the digital multi-channel surround sound etc - DTS or Dolby Digital