Building a house

1. Double wall construction with staggered studs (one wall's studs DO NOT touch the other, greatly reduces vibration transmission.
2. Line inside of walls with sheet vinyl. 
3. Double sheet rock on inner walls.
4. Electrical outlets close to ceiling to allow for wireless speakers. The more the better.
5. take steps to make heating/cooling as quiet as possible.
All I've got...

good advice given here... only thing i would add is to add a large storage closet to have room for extra stuff, and don't forget how you will do wall hangings, curtains and such for proper room treatment

https://www.homedepot.com/p/Siemens-FirstSurge-Power-60kA-Whole-House-Surge-Protection-Device-FS060/...

Surge protection at the electrical panel level

Don’t hit your thumb, it hurts.. I rebuilt my house and doubled the size, added shops and a basement.. I did it all by hand, by reading books and my family’s collective skills. Something about driving 99% of the nails by hand and fixing most of my mistakes.. No nail guns I couldn't afford them. They were actually not used by Union folks back then. Even the weight of the hammer. The more strike it takes to drive a nail the tighter the bind..
I used dipped galvanised nails. Harder to drive!! Won’t back out.

The electrical was easy for me. Every room outside the main structure including the attic and basement received 220-40 sub panels. I wired from there. Much safer and wiser way to distribute power too. Two separate, 120 legs add breakers as needed. I used 2 50s and added two more 100s per shop... Understand it is a collective load as per code.
I had a 200 amp main. I did some finagling with the inspector to get him happy.. (hid my wire feed) and covered a milling machine and lythe in a shed. ;-)

I recommend you put your hands on every piece of your new house. Look at it, understand what folks are doing, and NOT DOING..

DON’T settle, do it right. DON’T get sold a lot of shi$ you don’t need either.. Remember everything requires maintenance. EVERYTHING...

Here is the key to building your home.. ENJOY IT... Don’t let it happen make sure it happens.. You’ll love it...

Regards

Great responses already provided.Additionally details on points already covered, because these are very important besides other stuff and people need to pay more attention:
1. Size of the room and ratio of length, width and height is important. A ceiling height of at least 9 feet would be great.
2. As much symmetry in the room as possible - consider locations for speaker placement, chair placement and entry door. If you need to have windows, make sure that left and right side windows are symmetric, so that you can treat them equally.
3. If you can make the room sound proof, late night listening can be phenomenal.
Hope you post some pics once the room is done. Good luck!