Are you using a power conditioner? Sorry didn’t read every post. I own some PS Audio monos and it seems they prefer power conditioners to perform there best in my system. Cleaner bigger bass. I run passive conditioners. Some of my other solid state and tube amps the conditioners take away the bass and full presentation. With those amps I go straight in the wall. The difference is not subtle.
I tried subs long ago, didn’t know how to dial it in so had to let them go, since then haven’t been a fan of subs. Maybe if I knew how to set them up I would have a pair now.