The best and most elegant solution depends on how you want it set up and used.
If you want the most comprehensive solution, but not the cheapest, you can either build or buy a HTPC (home theatre PC or shuttle PC, etc) and run that. It will be the media hub for music but also means you can display networked movies via the TV as well.
If its all a bit too elaborate, then you can just run an old PC and connect it to an amp or hi-fi via the line out. Any old PIII or Celeron will do. Even better if you can run MCE on it and use a remote.
The most elegant solution would probably be a specialised hi-fi device, like
this although you'd need to confirm it does NAS.