Welcome to the Forum! You are going to find a lot of really great information and help here. A couple of suggestions. You can edit your photos in in photobucket to re-size them for message boards so they are easier to view for curmudgeons like me.
Is sound isolation a concern of yours? Keep in mind that it is more than keeping the audio in the room from going into the rest of the house. It is even more important to keep outside noise out of the HT while you are watching movies, sports, etc. If you do want to isolate the room, you will want to get the drywall, green glue, etc installed before you build the riser and soffits.
Good luck and have fun with the process.
ChrisMy Build ThreadStarting Drywall"Fat, drunk and stupid is no way to go through life, son."