Am I correct in remembering that multi-channel SACD or DVD-Audio discs only played through analog inputs due to some copy-protection issues? Much as I'd love a new receiver to update my system in the new house, I don't want to lose SACD and DVD-A playback capability.
To play the SACD/DVD-A format, the analog connections were required but if you switch to a digital connection, the discs should have a Dolby Digital equivalent. I used to A/B the difference between Dolby and the DVD-A format during home auditions for people. I probably even left a review on these forums about it, oh maybe ten years ago.
Just checked wiki and yes, the sound goes to the video data portion of the disc where DD5.1 gets played back.https://en.wikipedia.org/wiki/DVD-Audio#Player_compatibility
If you want to hear the difference, setup your DVD-A using analog on one input on your AVR, then connect the digital to another input on your AVR and you can A/B back and forth between the two inputs. Note the SPL playback volume could be a bit different so you might hear a slightly louder sound via one of the inputs over the other. Don't assume it sounds better but rather listen for differences in the location of vocals, instruments. I found the biggest difference was that.
If i recall the DD5.1 sounded more immersive, like you were sitting with a band playing all around you whereas the analog format sounded more upfront like you were sitting in the front row of the auditorium.