A universal player is not ideal for playing music. If you are serious, you should look at a CD Player. As has been mentioned many times before, even a inexpensive CDP from companies such as Marantz, CA, etc would be better than an universal player.
The difference between Oppo's 80 and 83 are in two areas. One; the 83 has a much better circuitry for audio. Second; the 83 has a class leading scaling engine for DVDs. So if you have a large set of DVDs, the 83 will serve you better. For Blu-Ray as such, either will suffice.
Cheers