Well, sorry to say that, but your Belles amp probably is not a good match for the LFT 8bs to say the least (some would say it is distinctly mediocre, but we all hear differently I guess) .... That is a first time I hear panel distortion of the LFT 8s, or the bass issue you have described, and I ve heard about dozen of ET 8bs and ET 6 installations. The room and improper placement is usually the culprit. Also people using jumper cables instead of true bi-wiring affects their sound to the worse. Did you tighten the panel with hex screw driver as per ET/or your dealer instructions? The tightening (but NOT OVER tightening) makes a HUGE difference in the overall sound quality of the LFT 8bs... If you like solid state amps you should try once in your lifetime to buy used Electron Kinetics EKSC 2a stereo amp and pair it with LFT 8bs...
I ve pretty much heard all Martin Logans ever since late 80s, and the only pair that would match or better the LFT 8s (not to mention the superior, sadly long discontinued model 6s) in overall coherency, wholesomeness , realistic timbres, the ability to portray recording venue with realistic proportion, the freedom from having to sit smack in the middle with once’s head firmly affixed in one position was that model that features wide panels plus woofer towers, a la Infinity IRS... and those were about 25 grand back in early 90s....
The only speakers in my (NON) humble experience that would match or exceed the LFT 8bs performance in spatial, tonal and dynamic nuance would be Apogee Divas, and Apogee FRs, and Eminents own 6s... in a very large room.... The LFT 8bs can be magical even in small to medium size rooms...
Being one of those obsessive music lovers that like to own as many different speakers as possible, I was considering the purchase of new Bowers Wilkins 802d3, or 800D3.... So I went, and I listened, and I listened, and I liked what I heard ALOT... Then I returned home and after hearing the same music on my ET 8bs even in my second, less than ideal, small listening room, I could hear that the most excellent B&W were NOT as fast, natural, delicate, open and spacious as the LFT panels.
.... There is an audiophile in princeton, nj that has ET 6s with the Nestorovic subs with two pairs of german Symphonic Line 4 monoblocks with separate crossovers in a spatial room.... I ve travelled far and wide all over the world for work, and was able to listen to systems at different audio shows, and to the million dollar systems in homes of Russian oligarchs, but none of those were organic enough, or able to match this Princeton Eminent Tech based system.... . Bruce Thigpen IS a genius!!!!!!
So, yes, in essence the Eminent Tech 8bs are reference speakers, for ALL the possible musical genre as my 20 000 albums collection can attest.... if you know what the properly recorded music sounds like ;)