Hi, I had a DV 50S for a few years. They are great players. Honestly, you're going to have to spend some money to get better play back. And a external DAC will loose the SACD (which is really nice on this player).
I'd either step up in the Esoteric line or maybe try a dCS Puccinni. Again, it's a bit of money to really get a improvement...
I wish I'd kept my DV 50s for dvd's...