In your stated price preference:
I'm a former owner of Quad ESL (what people now call "ESL-57) and ESL63. Particularly if you prefer the 57 over the 63, I think you will not find satisfaction in a crossover-based dynamic speaker. Of that sort, consider the Spendor S3/5 in either of its voicings. This is one of a few speakers able to legitimately claim to be a modern update on the venerable BBC LS3/5a monitor, and is probably the most neutral among them.
However, I have two other, more pertinent suggestions in crossoverless speakers that have the behavioral unity and speed of the Quads. One option is the Zu Omen speaker. THey take up about 1 square foot of floor space and can be ordered or found used in a variety of stained wood colors. The Zu Omen is friendly to SS or tube amps. The Omen is built around Zu's 10" full range driver supplemented by a supertweeter above 12.5kHz on a high pass filter. At 98db/w/m efficiency, Omen is easy to drive with a modest power SET tube amp, will handle much more power from push-pull tube amps, and it puts solid state amps in their sweet spot.
A second excellent option, if you stretch your budget just a little, is the Audience 1+1 micro-monitor. This uses the astonishing Audience full-range driver. This speaker delivers all the behavior unity of the ESL57, without the beaming, and despite its tiny dimensions is less limited dynamically than the much larger Quad.
For anyone looking for Quad ESL-like sound and unity behavior in an aesthetically discreet speaker with high spouse acceptance factors, I think the Audience 1+1 is unbeatable. $1800/pair. It was pushing out one of the best sounds at any price, at the recent Newport Beach show.
Phil