rhcorolla, I can see two options for using the BDP-83's analog output.
One option is to use the stereo analog output, either to a stereo analog input on the Denon (assuming it offers an "analog bypass" mode that would preserve the analog input) or to the Ext In left/right connections (if there is no "analog bypass" mode for stereo inputs). In this scenario, there would be no bass management at all (no subwoofer signal) and no Audyssey.
A second option is to do what you originally described, connecting six RCA cables (or at very least three - left, right, and sub) from the BDP-83 to the Ext In connections. The BDP-83 would provide bass management using the fixed 80Hz crossover, but there would be no Audyssey. By connecting a set of six cables, you could also compare this path to the digital path for multichannel discs (DVD, Blu-ray, SACD, DVD-Audio).
The trade-offs of analog vs digital will depend on several factors, and since you have Audyssey in your receiver one of those will be room acoustics. A room that benefits greatly from Audyssey correction will be more likely to yield better sound with the digital connection. On the other hand, a room that is fairly well-behaved to begin with (and thus benefiting less from Audyssey) will yield different results. In my BDP-83 review, I noted that I was surprised when my wife observed that CD's sounded better via analog output than digital. My Onkyo 885 processor also employs Audyssey, but the benefits of electronic room correction and EQ in my room are not as significant as in some other cases because the room's acoustics are pretty good to begin with.