Well, two things:
You listed your gear but I am not familiar with any of it (which doesn’t mean anything as a couple of decades ago I quit keeping up on this stuff) but I did find in the decade before, that as I gradually upgraded the electronics in front of my speakers, everything (sonic-wise) got bigger, better, and tighter. I said I have been out of touch for the past two decades and that is true, but over the last three years I did splurge on a new SACD player & a preamp I could not afford and, sonic wise, things are at the best they have ever been. (But, sadly, I am still not having as much fun as I had about 25 years ago.)
Secondly, I read through this entire thread starting yesterday, but I can’t remember if something like this has been proposed, but maybe start over with a clean small equilateral triangle of about 4’ in the CENTER between walls and then start increasing it by equal increments and see if you can find something. Since that equilateral triangle will start out small, keep the back wall clear of gear and obviously no gear between your speakers (everything off to one side). I think I would start out with keeping the rear wall clean as well (if it was me).