My question is: do you think the new Oppo BD player would upconvert standard DVD's better than my Marantz and/or improve the BD quality as well over the Panny?
I skimmed a review of the Marantz. It seemed pretty complementary, but the lineage of the BDP-83's DVD performance is hard to argue against. If I had to predict a winner, I'd come down in favor of the BDP-83. I think that barring a setup mistake, there should be no reason for the BDP-83 not to at least equal the Marantz. It would probably even exceed it, although we're probably getting into the domain of diminishing returns so I wouldn't guarantee something totally mind-blowingly better.
As for Blu-ray performance from the BD55 versus the BDP-83, in theory there shouldn't be any apparent difference. Both should simply "get out of the way" and pass the HD signal cleanly.
The beauty of the DVD-A format is it IS the DVD format. Any standard DVD compatible player SHOULD play it. I've only seen one DVD-A not play and it was in a friend's Pioneer Elite DVD player. The same DVD-A played in my old Sony DVD player and my new Samsung BD-P1600.
Yes, and no. Yes, a DVD-Audio disc may
play on a standard DVD player, but unless it supports DVD-Audio (which includes neither the Samsung BD-P1600 nor any Sony product ever built) you will
not get the losslesss audio offered by DVD-Audio's MLP. That means you're missing out on the main reason that DVD-Audio exists. To really play DVD-Audio and get the benefit from it, you need a player with DVD-Audio support. The BDP-83 has that support with the current EAP firmware, although it's still pretty rough around the edges. I expect the next round of EAP firmware to improve matters in that regard.