Wow. Buy a regular solid core door on sale for $75, or buy a steel solid core for $150, or buy a steel solid core door with a 7.25" jamb (to account for the 2x6 wall, plus the 3 layers of drywall) and it jumps up to $400+.

I might do with others did and create my own jamb extensions and if I need to add mass, I can add a 3/4" sheet of MDF to the part that is inside the theater and cover it with an acoustical panel or something.

Farewell - June 4, 2020