I always wanted a personal screening room, but I don't think I will be rich enough to do this in my lifetime. Flat screens are cheap now added to a 5.1 or 7.1 surround sound system would sound awesome in a log home. Nothing to rattle much but the windows.
There is always sound insulation that you can buy if you want to separate the sound from different rooms or if you don't have the money for that the normal fiberglass insulation is better than nothing. I would do that to the bath rooms for obvious reasons.
I've checked out a few home theater design places and many of them have great DIY ideas or at least give you a clue on where to get started. If you have a chance to check it out this place really caught my interest.