Personally, I don’t spend on upgrades unless there is an acoustic reason. Otherwise, the money is wasted. I agree that all rooms need acoustic control because the room and system are inextricably linked.
As for brand names, I am going to disagree a little bit. While some market products by taking advantage of the narcissistic consumer, I think some designers understand acoustics. After all, acoustics is part of a division of engineering, and engineers build audio equipment. Not every brand markets only on the assumption that their customers don’t understand acoustics -- or don’t want to. This forum is filled with consumers who care about acoustics. And, we could list many audio brands whose designers understand acoustics.
That does not mean that these engineers always try to solve the room for the listener -- but there is more than one speaker manufacturer out there that tries to offer placement advice to their customers, right?
And then there are the engineers who design acoustic treatments and offer guidance (such as GIK). Those are "brands" that use their knowledge of acoustics to help customers.
"In my experience, an optimally controlled, low-cost system in a room designed for it will generally outperform a more expensive, out-of-the-box system in a typical living room."
Agreed. But I also think you are on very correct ground to claim that a $1000 system in a great room can beat a $100,000 system in a bad room. That is how much we agree that the room is important.