Have you seen what a bucket of Green Glue costs? $330 roughly. If it's only 1 wall, it's much cheaper and way less labor intensive to use Quietrock. You fill the back wall with Roxul insulation and then just a single layer of Quietrock. Quietrock suggests not using the channel because of its weight. Make sure no air can get through either so sealing all outlet boxes and such are necessary.
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I recently had a room built in the basement and used Green Glue between 2 5/8" sheetrocks for 1.3 walls. I say .3 because one of the walls had to be extended a bit to make the room bigger at that end. The rest of the walls were finished and there was already dry wall in front of concrete. For these newly done walls, I used the 2 sheetrocks and Green Glue on BOTH sides of the 2X4s. Also has insulation between the inner and outer walls. The noise level is very low. In fact I did not have an option, but to build the room next to where the furnace is. But with this wall in place I can barely hear the furnace, when it is turned on. I am pretty happy with the room.
I used Green Glue on the ceiling when I finished my basement for a theater. It does a very good job of stopping everything except low bass. The bass gets through the ceiling, through the joists I presume. Your staggered wall should help reduce the bass significantly. There is a lot of discussion on using Green Glue in the Home Theater section of AVS Forum. Unfortunately, I have seen a lot of discussion on sound isolation but very little on the effect it has on the sound in the room. You might check the AVS Forum, since it has been a while since I followed that forum.
It sounds like you have done your homework, but if you need more information check out this website which discusses various techniques and products.
Sound Isolation Company