Has anyone used "Quiet Rock" sheet rock in room?

An interesting somewhat less expensive idea would be to use the DENSARMOR sheetrock. It is paparless and mold resistant.

The reason I mention this is that we did a re-model for a client and used regular half-inch rock on some walls and the DENSARMOR in the bathroom. He installed wall speakers on both kinds of sheetrock. Just putting my hand on one wall, then the other, it seemed that the DENSARMOR vibrated a whole lot less when playing music from the wall-mounted speakers.

Not scientific, but food for thought. Oh, this stuff is available at Home Depot. You can google DENSARMOR and decide for yourself.

Unclejeff--that's interesting and we will actually explore some possibilities of using that in combination with a layer of sheetrock and green glue in between. Same material layers (5/8 sheetrock) with green glue in between give really incredible results for $ spent. I think we may do some experimentation with this Densarmor board. Is it similar to blue or green board?

It can replace normal sheetrock or greenboard. My contractors are using is throughout the job. It has a paperless backing so it is not receptive to mold. There is some fiberglass involved, I think.

Again, my own 'test' is one of a field observation, nothing else.

Field observations are sometimes where discoveries are first made. We regularly learn things from builders and then incorporate them into our plans so that everyone benefits.