(My habit of downloading user's manuals may be helpful in giving more specific answers for your components)
First, you don't want to try to send hirez audio tracks, even two-channel, over the optical digital or coax digital (SPDIF) outputs. Either you will get no sound, or, for a copy-protected disk, the sound will be there but the 176 kHz 24-bit tracks will be down-rez'd to 44.1 kHz 16-bit, in other words "mere CD quality". (See table, "Sound output from ... digital audio output", on p. 13 of the Denon 2910 manual.)
The simplest way to listen to the two-channel DVD-A (or "advanced resolution stereo") recording is the same way you already listen to multi-channel recordings, via the 5.1 analog connection from player to receiver. Then you will get sound out of the left and right main speakers, and also redirected bass (below 80 Hz) out of the subwoofer, assuming bass management is set up in the player. Just think of it as a 5.1-channel recording with silence on most channels
But with a two-channel high-rez recording, you also have the option of doing all the audio processing in the receiver, rather than the player. I suggest that the best way to do this is: first, connect a pair of RCA cables from the two-channel analog outputs on the player (next to the 5.1-channel outputs) to any unused two-channel analog inputs on the receiver (on your model: Video 1, Video 2, Video 3, CD, or Tape, they're all the same). Second, set the receiver to play from the inputs you just connected. Third, turn off bass management and other processing (such as speaker delay and level settings) in the Denon 2910; I think this is most simply done by selecting Source Direct in the Audio Setup menu (remember to turn Source Direct off again when you next listen to a multi-channel recording). Now you are ready to use the bass management and other options of the receiver.
With the above steps, you also have the option of using Dolby ProLogic II(x) or DTS Neo 6 to create simulated surround sound from any two-channel recording. (I think this is a matter of personal taste, choice may vary with recording or mood, i.e., is today a Prologic II, Neo 6, or two-channel stereo day
"Purists" might point out that the "audio processing in the receiver" option involves an extra A-to-D and then D-to-A conversion (because the audio signal is sent as analog to the receiver and then internally transformed back to digital to do the processing). I'd suggest that the A-to-D and D-to-A chips (on pretty much all modern receivers) are sufficiently good that the extra conversion step does not harm the sound quality; you can judge what sounds best on your system.