Joey, sounds like you have a great plan so far. The one weakness I see would be the door to the room. The rear wall being stagger studs will help isolate, but if that door is think, hallow, what-have-you, it will almost make all the work for the rear wall a waste. I know from experience on this. My rear wall is very quite, but the double french doors with single pane glass, HUGE WEAKNESS! I won't make that mistake again. Look into buying a heavy duty, exterior door that is rated for sound and even fire (helps with sound isolation).
The flex tubing for your HVAC is a solid choice. I'm sure you know this, but just in case make sure you create a few bends in the tubing to help reduce any sound that does try to travel that path. But make sure the bends are not sharp enough to reduce air flow.
My only other concern would be the wet bar area. There is a good chance since it is in the rear of the room and in/near a corner, it could be a huge area for bass to load. An idea would be to somehow close that area off using the existing closet doors or maybe some bi-folding doors. They don't have to be as solid/heavy as the other door leading to the hallway, just enough to reflect the bass and keep the bass for getting caught in that back corner.
If you have any other questions, feel free to PM me. But I think you have an excellent idea and plan so far! Keep me posted.