If you're interested, you can check out the construction of my place, Spectre Sound. Essentially, we went with a two-room side by side design based around John's plans. Here's the links: http://www.spectresound.org/construction%20list.htm
This link is up on homerecording.com's bbs as well, so apologies to the moderators!
Spectre Sound
Originally posted at johnlsayers.com, topic 276.