This is the rabbit hole in which I seem to live!

My current solution is a Marshall 1965B 4x10 cabinet with the original G10L-35s, rated at 94 db each. Unfortunately the benefit is lessened by having 4 of them in the box, though still a little less loud than the G12M25/75hz in the combo. I do actually have and use a Weber MiniMass attenuator mounted in the combo cabinet and the 5E3 seems to be one the few amps that doesn't mind the mild use of an attenuator very much. Once you really squash it down though, all bets are off!
It seems that the only real solution for using amps in their "sweet spots" may be FluxTone speakers, though I really can't justify the $1,275, or more for the experiment!
https://www.fluxtonespeakers.com/products/
Eminence made their own "variable flux density" speakers in both British and American voiced versions, but I've never tried them, as they only attenuate to 92 db and have been discontinued. Not sure if the "discontinuance" was because they sounded like doggy doo-doo, didn't attenuate enough, or........? There are still a few out there on the market, but only in 8Ω versions:
https://www.sweetwater.com/store/detail ... aker-8-ohm
https://www.sweetwater.com/store/detail ... aker-8-ohm
Just My $.02 & Likely Worth A Whole Lot Less!
Gene