In the east coast states Crutchfield is the opposite they are knowledgeable and helpful and they sell everything you can want —unless your into weird esoteric stuff but then your gonna get weird snobby people selling it. I use them as well as world wide stereo and audio advice. They’re all pretty great and ship anywhere in the country with free returns.
I run Apple Music, to WiiM mini, to schiit modius, to marantz all analogue receiver+monitor audio silver 100. Sounds fantastic.
To get a rectangle and retain space for storage, tools or whatever else, why not bisect it with framing/drywall and make a smaller, rectangular room. You can then apply the great suggestions everyone else is making to a smaller space and get more bang for your buck speaker and amplifier wise. Just an idea and no idea if that’s more of an intervention than you were planning!
You are preferring the present to the past.