I had Quad 57s for several years. I used 50 Watts/ch tube Amps with power supply mods and aircraft quality output tubes to drive them with no problem, ever. Bass response and overall dynamics of the Quads were very impressive, especially compared to their rather uh, tame stock performance - but only after I removed the metal grills as well as the plastic dust covers and placed the Quads on Arcicci stands. I playing LPs on a Special Ed. Maplenoll Ariadne air bearing everything on a special version of my own sub Hertz pneumatic isolation stand that was modified to accommodate the super heavy Maplenoll TT and around 100 lbs of ballast.
Quad ESL 57 playing Prince
I have a great pair of quads. I always feel that playing really tight bass like a Prince album can't be good for those panels (not too loud!). I just listened to "Sign of the Times" and the speakers played fine. Are my reservations baseless??