Many years ago, in the early 90s, I went to a dealer in Hudson Valley (Mount Kisco) who had a pair of the strangest looking loudspeakers I had ever seen. I had no idea what they were, but he played me an LP on them. I was gobsmacked. They didn't sound like any of the usual hyper bright moving coil multi-driver speakers I had heard. They sounded like nothing I had heard. Of course, I promptly figured out a way to buy a pair of them. The speaker in question of course was the Quad 63. In many ways it solved the problem of producing sound pressures in a room from input voltages that is inherently linear, and still remains amongst the lowest distortion truly phase linear speakers you can buy -- 60+ years after Peter Walker first started working on the concept (hence the moniker "63", which dates to his earliest notebooks).
My most recent speaker acquisition is many times the size of a Quad 63, and many times its price: the Soundlab G9-7c, which is over 9 feet tall and 4 feet wide. It has confirmed for me that the surest way to get off the hifi upgrade treadmill is to invest in musically accurate loudspeakers. The rest almost doesn't matter. Of course, as someone who had just graduated with his PhD in AI in the early 1990s, I could not afford the then Soundlab A3 that Gordon Holt raved about in an early Stereophile review. Those days, AI researchers were not paid 7 figure salaries, as they are now in the Bay Area! No one knew what to do with us! But, times have changed, and my bank balance certainly has! Hence, my ability to afford the G9-7c's.
I still have an original Quad ESL (57), which I listen to every morning. No, it's not as awe inspiring as my G9-7c's, which drops you into the powerful thundering sound of a symphony orchestra, but in its own charming way, the 57s still get the gestalt of the music right that defeats almost every other multi-driver dynamic loudspeaker that seem to try to dot all the i's and cross all the t's, but somewhere in the morass of getting all the detail right, the music making is lost.
Dealers who teach you about good products are rare and worth finding out, but it's more luck than anything else in finding them. It's usually the small shops, rather than the big glitzy ones, where you find the true gems.