I noticed that Rhino Handmade has started releasing what they call Quadio DVDs, reissues of some of those quadraphonic LP mixes from the 70s. The first Chicago album came out earlier this year. The Best of Aretha Franklin will be out soon.
http://www.rhino.com/article/what-quad It says DTS DVD, so apparently they’re not high resolution. They’re just lossy DVD-videos...with no video. It seems like these would have been better suited to DVD-A or SACD. The $30 price tag seems awfully steep too, for what you’re getting.