One of the most challenging issues is controlling sound in the home theater / studio. We want to be able to watch a movie or record live drums in the space without a major amount of sound being generated outside of that room. Now I realize that getting it absolutely soundproof is not within reach of the conditions we have to work with, but a reasonable amount of reduction and isolation from outside noise should be possible.
The key factor here is actually doubling all of the walls that adjoin another room or that are not 6 inches of concrete (which two are). The other thing is decoupling the ceiling from the floor joists which is done with something called resilient channel. It turns out that one other thing that helps is using metal studs to frame the space. I was hesitant to do this, not knowing anything about working with them, but I took the plunge and wow what a great way to frame a space. All I can say is that working with metal framing material is fast and clean. No sawdust and quick cuts without running back and forth to the saw. Walls go up very quickly and the task of boxing around duct work is much less painful.
I have about half of the framing done and it has been very enjoyable. I will post some pictures and detail the progress as I go to document the process.