-Upfront disclosure, I represent Quiet Solution, so I know the products well-
QuietRock is available in 3 product levels, all the way up to the THX certified QR-545 and is sold at 300 dealer locations nationwide and in Canada. It is not sold direct, so there is no "shipping charge" per se. QuietRock panels are manufactured in California and shipped to distributors nationwide via rail.
You do NOT need any special mud or special mounting devices or special membrane or anytuing else. You hang and finish QuietRock panels just like regular drywall. There is a video on the front page of the website that shows this. And the 5/8" product (QR-530) weighs about the same as standard drywall. It isn't about weight.
QuietRock is a UL certified product that increases STC value in any wall assembly (single, staggered, or double stud) by using contsrained-layer damping, not by using mass.
There are hundreds of independant field and lab tests, and many lab tests in many configurations are published on the website.
The QuietRock QR-545 THX panel (which is the highest-end product made by the company) has been tested in assemblies to STC-80 with losses of 50dB at 50Hz.
QuietRock QR-530 is more expensive than drywall, but almost always the least expensive method to reach higher STC values. For instance many people use mass-loaded-vinyl which costs $2 to $3/sq foot delivered, but the wall only tests at STC 43 in a finished single wood stud assembly with MLV in it (there is a white paper on this independant lab test on the site as well). QR-530 is about $1/sqft more, but delivers a testsed STC 52 in the same wall (without MLV of course).
While QuietRock is certainly used in home theaters, QR-530 is most popular for large multifamily builders to build party walls that meet the required STC 50 code. QuietRock on one side of a single stud wall is the least expensive method of meeting STC 50+. But of course large builders have to consider labor costs, risks, failure liability, (and they get better pricing for large volumes), so for them, QR-530 may be an easy low-cost option.
