Aesthetically pleasing room & good sound is THE biggest challenge.
While I get having a "listening room", most just aren't guest friendly-something to have your non hi fi over friends over, for a sit in.
Everyone's idea of a "good looking" room is different. While not ideal, a windowless room and sound treatment with audiophool gadgets is not my bag. Those one/two seat setups are especially disturbing.
A Home theater is completely different situation as far as windowless, sound reinforcement.
Get the best gear you can afford with speakers in the best location, minimal intrusive acoustic treatment in a beautiful room is where it's at.
Pour more drink/ingest more consumables to get over audiophool deficit in your guest's glass to make it sound "better".
Someone who can develop wall/ceiling sound damping/diffusion panels that are invisible and removeable would make a small fortune.
