I have owned Quad ESL-63s electrostatic speakers since I imported them from England in March of 1985. I imported Quad amp and preamp at the same time but eventually replaced the electronics with a tube amplifier, an Audiomat Arpege integrated amplifier from a French company that is 30 wpc.
I should mention the reason I went to Quads in the first place was due to a chance reading of an article in Opera News that Quad Electrostatic speakers were the ideal speakers for opera lovers. I love opera music and I love classical music and my experience suggests that the author of that article was absolutely right. Quads are ideal for listeners who especially love the mid-range. Voices, violins, piano, cello, guitar, etc etc sound so utterly natural and beautiful as though live in the room with you. I eventually upgraded to an Audiomat Prelude Reference MKII, another 30 wpc tube integrated amp that was an Arpege improved. Just a wonderful integrated tube amplifier. I also played with putting my stored in a closet Pioneer SX-1050 with 120 wpc to my Quads before I decided to buy the Prelude and it sounded great but I was worried about putting too much power to my beloved Quads, so I decided to go with the Prelude. Besides, the Quads seem to be made for tubes. That is their natural partner.
In 2017 I had my Quads completely refurbished. What a treat to listen to them!
Many wonderful years later, I happened to audition a Luxman Tube amp and preamp that sounded beyond wonderful with my Quads. Well over my price range of course, but I decided to buy them anyway.
Then along came an opportunity to buy the US Monitor version of the Quad ESL-63s. This from a friend who was downsizing. He had just bought them from a refurbisher of Quads, so they were almost liked brand new!
I have been invited to listen to the systems of fellow audiophiles and so far my system sounds better than some costing thousands more. I attribute this to my Quads and their ideal pairing to high quality tube amplification.
The only way to criticize them is to knock their base. they don’t have a great bass but, honestly, I’ve never minded. I could add a sub, but I haven’t found it necessary. I’m now 85 and I like to joke that I want my Quads buried with me.