A more thorough opinion on them, and the Harbeth SHL-5s.
I find it really hard to write about these speakers in a way that I feel conveys how they sound. A lot of things in this hobby are variations on the same theme. I think a lot of current higher-end speakers fall into that category. There are ones that I like and ones that I don't like, but they exist within guardrails of what I expect a speaker to sound like. And, of course, we all have a taste for things that has evolved over years of listening and us getting used to one sound over another, to the effect that what I love won't necessarily be what you love (take that, objective-only-reviewers...we get used to things).
I can say that I own these after auditioning speakers all over Chicago and LA back about 7 years ago. And I made the decision to buy them, after hearing all of those speakers, after hearing one song. I listened to more songs on them, but I knew within the first song that I wanted these speakers. They had the sound I'd been looking for, and not finding, in every other speaker I'd heard. They just didn't sound like speakers. They still don't sound like speakers. Music just sort of hangs in the air, its weird. They present a texture to the sound, I wouldn't call it 'detail' so much as a tangibility to the sound. Things feel real and fleshed out and right there in the room. It's like there are no speakers, just sound coming from air.
So why do I have and love Harbeth SHL-5s, which I bought soon after these 'perfect' speakers? Well part of it is, back when I got them, I had room for two large systems. But part of it is also that they're not the most livable things. You have to turn them on. Turn them off. They need to be a fair bit out from the wall. They're, ahem, not the most attractive things. Every non-audiophile who sees them notices them before anything else in the room. "What are those things?".
And so I got the Harbeth SHL-5s to be the presentable speakers for a living room system. And I picked them because, of all of the speakers I had heard they sounded the closest to the Quad 63s. They do sound a fair bit alike and do some things like timbre accuracy similarly. They both give enough detail to sound lifelike, without becoming one of those speakers that the first thing you comment on is, wow, they're detailed. They both cover around the same range. There is just, with the Quads, an extra veil removed..and the SHL-5s are not veiled. Its just, they aren't Quads.
They aren't for everybody and I have to think that condition plays a HUGE part, for I know at least one person with similar taste to mine that had a pair and sold them quickly, a stock unrestored pair. Mine are not stock. Also, these are PRO versions, stiffer, more robust in both build and their protection circuits compared to some 63s (I had a 400wpc amp on them, handled with volume-caution, with no hiccups, no clamping, no shut downs..these are not like 57s in that regard). They have all new panels from about 8 years ago. Everything was reconditioned. So maybe this pair is a unicorn. Whatever it is, they're the finest speakers I have ever heard for my taste, at any cost. Which is why I've kept them, even though I don't have a permanent place, yet, for them.