Quad seem to have dramatically improved on the volume / dynamics problems since the ELS63. I was so impressed by a friend's 2905 speakers that I bought a used pair myself - ones that had been upgraded with 2912 transformers - I understand that's the main difference between these models.Quad ESL63 - Wonderful in all respects other than the limited maximum volume/dynamics. Very frustrating that the protection circuits kicked in before 'realistic' volume levels could be reached and/or when music with loud transients was played
Quad ESL63 again but with accompanying Gradient Subwoofer and active crossover. Superb, much better than sole ESL63's. Only got rid eventually as I was fed up with failing panels, otherwise would have been a speaker for life.
My room is huge at 945 sq ft and I was then using big Avantgarde Uno horns that feature twin 10" drivers each side. To my great surprise, the big Quads were able to play as loudly as I even wanted and the bass was a revelation as I'd expected it to be lacking. No need to consider subs.
I never intended to keep these "barn doors" because of their centre-room placement, but they encouraged me to look at other slimmer electrostatics. I bought at vast cost, Martin Logan Expression 13As new, but these turned out to be a serious disappointment, but only because of their uncomfortable placement in the centre of a room with 12 ft behind one and 15 ft behind the other - with a floor-to-ceiling glass wall behind - at an angle! Why the Quads coped so much better than the MLs is a mystery, but the MLs were sold and new Avantgardes procured.
New big Quads are a bargain given their performance levels.