The sub panel is a great idea for convenience’s sake. You can run a 60 Amp circuit with 1 cable, and then have short runs to the room, giving you a number of dedicated outlets. If your listening room is far from the main panel, this is going to be a great, flexible solution, and may be cheaper than attempting to run multiple lines. Also, all your grounds will end at the same single reference point int he subpanel.
It may also be a good idea to update your panel. :)
And, if you want to go totally nuts, you can even put balanced, isolated power before the subpanel. :)