Yeah, concrete's daunting, but it's really just one big effort then a few hours hanging about waiting for it to turn. IMHO a far better solution than timber regardless of sonics.
I would really look at installing weep vents before proceeding with the studs. I know I'm like a scratched record, but they're easy to install, cheap and provide an exit for any water that materialises, either through rain penetration or condensation https://www.ebay.co.uk/itm/Brick-Wee...QOCBgo7zWnTyZw
I take it you'll be installing a dedicated electrical circuit for the HiFi? Again, I'd highly recommend starting a new thread for input from those far more knowledgeable than me. My advice would be to install a Radial over a Ring, terminate to one point and star out from there and do whatever you legally can to avoid fuses.
For me installing a dedicated Ring was a step up, converting it to a Radial was another, but doing away with 3 Pin fused plugs was a revelation! If you look at the links below you'll see it doesn't need to be expensive and your spark will genuinely love wiring them. You will have to manufacture your own mains cables but it's not difficult, it's very cost effective and with these bad boys the world's your oyster when it comes to wire choice.
https://www.screwfix.com/p/abb-panel...-6h-ip44/6890f
https://www.screwfix.com/p/abb-strai...-6h-ip44/3967x