Since your DAV has an optical and coaxial digital in, you can just buy a Bluray player and use the optical/coaxial out of the player to connect to your curent DAV that will be used as an amp.

The only downside is that you won't be able to enjoy the HD tracks for that but just regular Dolby 5.1 and dts. For HD audio, you'll need to buy a whole new system.