What is the best way to hook up a Denon DVD-2910 ?

You really need to compare the built in DAC to the DAC in your pre. The 2910 has a really nice DAC. Hook up both R&L out as well as digital out and compare. There's no need to "turn off" the other channels if you are only playing 2 channel. What pre do you have? Any external DAC?

Some DVD-A discs have only a multi-channel mix. The Beatles Love is one such disc. If he was to play one of these with the other channels active he would only be hearing the front two channels of the 5.1 mix. Instead of turning the other channels off in the players menu, just set the player to downmix multi-channel DVD-A discs. Also obviously for both DVD-A and SACD he will not be able to use a coaxial digital out. He will have to use the left/right analogue outputs. Most universal players,such as the Denon, have duplicate pairs of analogue outs for the main channels. One just on their own, and one set that are part of the 5.1 analogue multi-channel outputs. I too have noticed that on some players the left/right front RCA outputs of the 5.1 hookup will sound better than the stand alone left/right stereo RCA outputs. Additionally I have found that often with DVD-A discs, even ones with discrete hi-rez two channel mixes,that using the player in downmix mode to achieve stereo will sound better than the discrete two channel mix. I have no idea why. Since you are adding the Denon player to your system, just simply try both hookup schemes, and see which one you find sounds best.

Thanks for the great responses. I have an Acurus RL 11 Preamp with Analog outs (no digital)a basic 2 channel preamp from 1995 or so. No external DAC. I want to get the best performance from the Denon playing SACD's (most of mine are 2 channel, but a few are Multi-channel) and DVD-Audio and some Redbook CD's (most redbook will be handled by my Jolida 100A/NOS GE5751 Tubes CD Player). I will try the Downmix Mode(I am asuming it is accessible on the menu?)and thanks for the tip on trying the download mix & stereo mix to see which is better as I would not have tried that as I would have assumed the Stereo mix would be better for my situation.