I did the Thermafiber but also wrapped my hvac above that area with butyl tape to reduce vibration transfer (think dynamat). The main run that goes above the theater area and up to the bedroom empties out next to the wife's side of the bed and she slept thru Black Hawk Down Saturday night.

Do the shower, you instantly move into a new category of buyers who search for 4 beds 2 baths instead of 4 beds 1 bath. (Or 4/3 instead of 4/2) but you know what I mean.

Consider mineral wool insulation too. I can rock my dual SVS PB2000 pros in my basement theater while my kids sleep upstairs.

I used thermafiber ultrabatt and it's amazing!

Yes, this! Put hardibacker up in it's place, and put new tile back up. You'll spend less time just tearing it all off then trying to be gentle and salvaging it.

Scrub it in real good and let it soak for a bit too.