I was watching a only slightly entertaining show called "Showdown of the unbeatables" and they featured this Accoustiblok that was able to muffle 140db of sound from the world's loudest train horn. This stuff is a flexible 1/8" thick polymer sheet and is supposed to be as soundproof as a 12" thick concrete wall!
Imagine what it could do for your rig, and even your house!! I'd like to know how it compares to some higher end stuff like dynamat.
http://www.acoustiblok.com/
German houses are made very solidly with cinder like blocks like this:
Then covered with about 4" of foam insulation, and finally stucco. There is also stucco on the inside. Couple that with very solidly made doors and windows and these houses are very sound proof. Even the interior doors have seals, which makes it nice to put the kids to bed and watch TV knowing they are not disturbed when Jack Bauer blows something up!
But the capability of this stuff seems amazing!