Grador and PENG, thanks for your quick responses-your interest inspired me to do a bit more research, which I have detailed below.
Grador, I agree with you with respect to the audio-since the audio processing is occurring in the respective receivers, the difference in DACs and analog output stages between the two decks is somewhat irrelevant. I found a thread here (using Google!) that states that the RX-A3000 uses the Burr-Brown PCM-1796 DAC, which is apparently their top of the line DAC, so I feel pretty good about the audio signal path (ie, BDP-83 via HDMI to the RX-A3000, then to the Rotels via the BBPCM1796). I can't find any information about the analog stage that follows the DAC, but given the quality of the DAC, I am hoping it is at least as good. As for the Denon, it has Burr Brown PCM 1791A DACs (one per channel), which are no slouches, either. In fact, the DACs in both receivers have dynamic range in excess of 113 dB, THD+N less than 0.001%, can sample up to 24-192 and have less than 0.002 dB output passband ripple (the 1796 is slightly better than the 1791A in the key specs). This is as good or better than the Cirrus Logic DAC in the BDP-103 (114 dB DR, -100 dB/0.001% THD+N, up to 24-192 sampling-no passband ripple spec to compare, though). The BDP-105 has ESS Sabre32 Reference DACs for the analog audio outputs (which are arguably the best audio DAC available today, with better than 135 dB DR and -120 dB THD+N, among other excellent features), which are the same as those used in the BDP-95 (PENG, this is why you probably don't hear a difference!), so the only two Oppo players that can offer me better audio performance are the 95 and the 105 (and that is only if I use the analog outputs and bypass the receiver DACs). Oppo's incredible customer service somewhat obviates the need for a new warranty-they replaced the drive mechanism on one of my 83s for no charge (other than shipping), even though the deck was out of warranty by two years (a BIG reason I am looking only at Oppos for my replacements).
The wild card is the video processing-I am not familiar with the differences in video processing between the Oppo and either receiver (or the newer units, for that matter), so that where I need to focus my assessment. For the most part, the other feature differences are not decision drivers for me, as I have other options available for video and audio streaming (Apple TV, Roku, Mac Mini servers), remotes (currently have a URC MX-980/MSC-400 and MX-880/MRF-350 remote setup for the media and living rooms) and network capability (already have a dedicated ethernet cable for both systems). The only capability I would like to have not currently available on the 83 is the ability to play larger video file sizes via the USB port-the 4GB limitation prevents me from playing my collection of 1080p video files via the 83's USB port (converted from my Bluray collection), which would be a nice feature to have; however, I can still play them via a software player in my Mac Mini video server (one of the main reasons I use the receiver audio DACs), so it is really a matter of convenience, not capability.
Grador, PENG, thanks again for your quick responses-I will try to post my findings in this thread in the event that it can help others with the same trade in mind.