Dudda

That new Gypsum board is very expensive and I'd say a sheet of ply/osb as a backing is cheaper. You could also talk to Gypsum*. They've a good technical team and lots of wall build up options including double layers of stud, acoustic board, resilent bars to improve acoustic performance, etc. Ask for the technical department not the sales department so you bypass sales reps and get the real answers. *I've no affiliation with Gypsum but I've rang them a few times.