best of luck to you, I hope you're able to design and build what you're after...we added a nice 'music' room as part of an addition recently, and having a dedicated music space is a great thing, and something I've worked towards for some time...
that being said, you might poke around this
Recording Studio Construction Forum. Looks similar to the TDPRI as far as different topics/forums related to building a recording studio. Pretty heavy on the 'professional' studio model, but alot of the audio principles are the same. Good luck!