I'm only guessing, but as the 5900 is Denon's flagship player, I'd hope it had better DAC's than their 3805 receiver. That being said, I'd opt to use a good pair of analog interconnects from the 5900 to the 3805, and playback CD's that way, rather than through the digital connection. I'd only use the digital connection for DVD (movie) playback.

And may I add...NICE GEAR!