While the James Taylor Beacon DVD is great, I must say the best sounding concert DVD I own is Eric Clapton One More Car One More Rider. It's a concert from the Staples Center in LA.
They must have had real high quality equipment there, since there is an excellent anamorphic widescreen picture, and the sound is just fantastic (including outstanding, tight bass through the SVS). Every bass lick and kick of the bass drum is tuneful and tight. Vocals are loud and clear and all of the different instruments come through nicely. Highly recommended.
I think the one mentioned the most is the Eagles Hell Freezes Over (rightfully so, it sounds awesome. Bass is amazing). My other favorites are Diana Krall/Paris, James Taylor/Beacon, and Norah Jones/New Orleans
JT also has another one named "Pull Over". After watching the credits, I then realized it was the show I saw him in Chicago (actually Rosemont Theater near O'Hare airport).
The Concert for George also has great sound. And the Alison Krauss Live dvd.