Yes, the 57s were great in resolving lightweight programme, ideally chamber music and especially the female voice in recital. But for other music they had poor dynamics, no 'slam' at all.
Few will disagree that if resolution is your first priority then electrostatic is the way to go. But since 1957 other companies as well as Quad have moved the game a long way along. I have used Martin Logan CLX Anniversaries for nearly 10 years now. Resolution just as good but with some muscle behind it. Still 3dB down at 56Hz though.