Other factors affecting sound

@holmz:

I swear plaster walls sound better than drywall.

Most definitely, though they are rare today. I was raised in a New England house with lath, horsehair, and plaster walls, and you can tell the difference just walking into the room. The random thicknesses of the plaster (and maybe the horsehair) reduce resonances, I guess. Wallboard is just a huge drumhead.

When having my own room built, I used QuietRock and kept an eagle eye on the sheetrock workers, who wouldn’t have followed all the specialized installation techniques (as specified by the manufacturer) without being pushed a little. They weren’t lazy; they just didn’t know.

220/240 sub panel, and # 12 copper romex for the 120vac receptacles. I use 125vac copper hubbarts. 

The thing I don't like about # 12 is roughing in all the pigtails. The best of days twisting wire nuts leave me crippled for a week. Not the good old days after 49 years of pulling wrenches. 15 minutes 3 sometimes 4 times a day, from 10-16 hour days for 49 years.

I don't use the basement or attic for sound but both have subs/220/240 and # 12/3/g copper romex. There are 125/25 amp outlets every 4 feet. I can add 220/240 to any outlet the wire is in there or split the two each having both L1 and L2 from the main in the box. L1 is always the left side of the room L2 is the right side. I don't mix the two. It can cause noise.

Regards

Hubbel receptacles look decent, not sure what Industrial vs. Hospital grade is. On amazon you can get them quite cheap, $20-40. 

I would suggest a whole house surge suppressor in your main panel.  (uses 2 spaces). Secondly, one or two dedicated 20Amp circuits to the site of your equipment stack. Third, I have used rockwool insulation in several recent remodeling projects. It comes in flat panels and batts. It has thermal insulation, fire resistance, water resistance, and sound dampening all-in-one. Usually available at HD and Lowes, but sometimes can be special ordered in larger quantities for a better price. Consider using rockwool above (between the joists) to lessen the sound bleed through to the rest of the house.

A basement can have heating issues, water leakage, flooding, musty smells, etc. Make sure that deal with all that as best you during your remodel.  best of luck.