Acoustic advice re: building a room (in wall or on wall) treatments

I am building an addition to my house for a dedicated listening room.  The room’s dimensions will be 20’ by 28’ with 12 foot ceilings.  I am trying to decide if I should treat the inside of the walls with Rockwool or similar product or forego that and rely on aftermarket “on wall” room treatments. I’m concerned that if I treat the inner walls, the room might become over dampened.  I would appreciate your thoughts.  Thanks.