Psyprof1 is right, room treatments will be key to good sound in a room of that size and what sounds like a square configuration. I don't know what you are planning for the ceiling, but you may want to consider some form of acoustical panels or tiles to help with the sound and to lessen sound transmission upstairs when you really want to crank it up. Insulation above the ceiling would lessen it further (except of course for that LFM-1).
It sounds like you're going to have a real nice setup between those 2 rooms. I really like the idea of the pocket doors. Good luck with your project!