Hey Cam, just looking at your pics I had an idea to help with the sound isolation. Can you have a 'frame' built around the backside of the shelves out of 2x4 or similar that you could use to insulate the sound. Depending on how it's built you could then put Roxul in that. And if built not too tight to the shelves I think you'd have enough room for air circulation too. I'll post a couple of sketches to illustrate what i mean (working on those now)

Dan
On-Wall M5HP LCR, QS8 & EP500 in 7.1