If you want the room to sound entirely neutral, avoid drywall entirely. Sound bounces off drywall, distorting the music as it reaches your listening position.
There are sound-absorbing wall materials that can render the room anechoic, and this will enable you to hear your system without participation by the room. You can turn your system up as loud as it will go, and you will be amazed at what it sounds like without echo in the room.
However, these wall materials can be difficult to work with, and may not be aesthetically pleasing, so you will also need to figure out some means of covering them that does not then bring back the phenomenon of sound bouncing off walls. If fabric wall covering can work for you, that might be best.
Merely putting the sound absorption material inside the walls, and covering them with drywall, will not do much good.
There are sound-absorbing wall materials that can render the room anechoic, and this will enable you to hear your system without participation by the room. You can turn your system up as loud as it will go, and you will be amazed at what it sounds like without echo in the room.
However, these wall materials can be difficult to work with, and may not be aesthetically pleasing, so you will also need to figure out some means of covering them that does not then bring back the phenomenon of sound bouncing off walls. If fabric wall covering can work for you, that might be best.
Merely putting the sound absorption material inside the walls, and covering them with drywall, will not do much good.