Having done that, my opinions are simple;
A good set of floor standers connected to pretty much anything will sound good.
Basic room treatment will go far enough for everyone unless you’re running a sfx studio or something and even then…
Anything over 320 mp3 is basically pointless, but the better masters you get on some of these 24/96 platforms make it probably worth the subscription (sometimes).
I prefer good headphones.
And this is how i’ve avoided spending 6 figures on audio gear :)
I agree with you on the untreated room and 60k amps (just buy hypex), I have a room that is designed by a professional and treated (massive traps completely covering all the walls and ceiling). Most people can’t dedicate the space to that type of setup though - particularly as it completely changes the look of a room.
But something like Trinnov can make a difference to even that setup - its what the acoustician will some days testing and tweaking particular as all speaker designs have flaws. Not that I have one yet, I didn't have the budget for it so I am making do with a cheaper alternative - but DSP for treated rooms makes a noticeable difference.