What vintage speaker might you use today

Ct0517, I would consider the Quad ESL-57 because of the legendary reputation it has achieved and maintained over the years, particularly with respect to its mid-range transparency. I am familiar with its impedance curve that you linked to. The wide variation from high impedances at low frequencies to low impedances at high frequencies, which is characteristic of many electrostatics, will of course result in its sonics being amplifier-dependent to a greater degree than would otherwise be the case. But as might be expected given that its design pre-dates the introduction of solid state amps, it is considered to be a tube friendly speaker, and tubes are my preference when it comes to power amplification.

Perhaps surprisingly, though, in some cases solid state amplification can also produce good results with that speaker. For example the vintage Mark Levinson ML-2 from the 1970s, which is rated at only around 25 or 30 watts into 8 ohms but can double its maximum power capability into halved load impedances down to 1 ohm, has always been considered to be a synergistic match.

Best regards,
--Al

LarryI, your speaker is hardly modest.  I am sure it sounds very nice by any standard.  My own vintage speakers are further down the scale.  As you may recall, I use a 15" Jensen P15LL woofer in a sealed cabinet similar to the Western Electric 753 with an Altec 802 driver in a 32A horn.  While I am sure it would sound better with a 713 driver, the 802 still sounds good to my ears.

Almarg
But as might be expected given that its design pre-dates the introduction of solid state amps, it is considered to be a tube friendly speaker, and tubes are my preference when it comes to power amplification.

yeah, the design predates moi, by a few years as well.
My actual pair of 57's are only about 6 years old. Fresh Wayne Picquet rebuilds. I am using an amp that was specifically designed for them. Music Reference RM10. Its been my personal experience that one needs to be very careful with their choice of music with them. My wife for example, seems to get suspicious, and keeps visiting me down in my space whenever female vocals are playing.

I'm going to have to agree with Al here, I have optimized a 1975 pair of Tannoy HPD's (12" Dual Concentric) with new surrounds, custom crossovers, and cabinets, and they perform equally well with 9 Wpc of SET power, or 500 Watts of Class D driving them.

They are better in every way than my previous speakers, Dynaudio Contour 5.4's, which weren't too bad either.

Douglas_Schroeder (BP), "Vintage gear is good for nostalgia trips and the audiophile on a lower budget (in fact, very good for them), but not great for building superior audio systems."

As I have often found arrogance the companion of ignorance, I could not disagree any more strongly with someone who doesn't believe the Quad ESL57 could hold position in the finest sounding audio systems.