I had the DMP-BDT320's predecessor, the 310. One of its best facets was its sound quality. I did back to back comparisons using the analogue outputs (so I was using the internal DAC and analogue outputs) of the 310 and my Cambridge 640C CD player into my old Cambridge 640A amp into Ruark Epilogue speakers (which were VERY detailed and revealing).
There was very little in it, not just in terms of dynamics and detail, but also the balance of the sound. The Cambridge just had the edge when music got more complex with more going on within the mix, but I'm really nitpicking. I had to play the same music excerpts over and over swapping between Panasonic and Cambridge to discern any difference and by that time it might have been my own imagination. So your decision might be based more on whether the Panny blends well with your Marantz amp and speaker combo. Synergy of your components is probably a more important consideration than the sonic merits of a particular streamer in isolation.
So the Panasonic's DAC is very capable considering it's a fairly inexpensive machine. However the above comparisons were purely using it as a disc spinner. I didn't use it for streaming because was only capable of handling mp3 and it required having my display on, which I wanted to avoid being a plasma owner. (Screen-burn paranoia).
So you'd just need to check the tech-specs of your bluray's manual to confirm whether your slightly newer player can handle FLACs and to what resolution. Obviously the Pioneer N50A adds Airplay and a couple of digital inputs which could prove handy for some.