DVD's with only audio capabilities...huh?

I was in Tower Records the other day and, next to the SACDs, I found a section of audio CDs that can only be played in a DVD player. It seems they are digitally mixed for a Dolby 5.1 format. They also said that these DVDs would sound better even on a two channel system as there is more detail recorded on them. I must admit that the music DVds have often sounded better than standard CDs. I bought three of them and I am playing them on my Marantz DVD player and using my Audio Aero DAC to feed a two channel system. The Audio Aero does register more information coming through than on a normal CD. They do sound nice, especially the Bachman Turner Overdrive, 'From the front room'. I came home and did a discussion forum search on Audiogon for 'DVD AUDIO' and found some talk about how good it sounds--at least as good as SACD. When I think about it, this system might have a better chance than SACD as so many people already have a DVD player. Has anyone with a really high end system tried this format...what do you think?