Do these speakers exist?

Thanks for the replies.

1) The Green Mountain speakers are absolutely killer. The C3 is quite a stretch for me at $17K and the Calypso is 88dB sensitive and 4ohms. Likely marginal with SET.

2) I used to have Gallo Ref 3s. They are 88dB and just don't cut it with 20W SETs in my experience.

3) I should have said no ribbons. Dynamic speakers only. No ribbons, no horns. I'd never heard an example of either that sounds SOTA for me.

Thanks again.

What about the GMA Pico models?

You might look at the line of speakers from Coincident.

I believe that the Silverline Sonata and Sonatina both fit your requirements.

I have an older pair of Sonatinas that I still use. Terrific looking, modestly priced, fullish range, high sensitivity and impedence, first order x-overs. Mine are very good, not great, sounding loudspeakers IMHO. I haven't heard the last few generations, so I can't comment on their quality.

Why are you even looking at 90db with an SET? Also, most amps don't have 6ohm taps??? Very few will be 4ohms and above 90db. You can not expect any type of performance out of a 20 watt amp with 88db. Stay away from thiels. They are amazing speakers but very hard on an amp.
Finally, a first order crossover put into this mix makes it tougher yet. If you can bend on the crossover, try Coincident Speakers. You will get 94db to 102db with a very flat 8ohms or higher and friendly to as low as 3 watt amps.
The other route you may want to look at is brand new Klipshorns. You will get flat to 25-30hz, over 100db, 3 way, 8ohms...

If you think 90dB speakers can't work well with higher power, 845 and up SETs, your experience isn't broad enough.

What you note about Thiels is apparantly NOT true of the new 3.7. They are supposed to be a much easier load. I don't know for sure.

I had always thought 1st order xovers were the EASIEST load for an amp. They are the simplest crossover - fewest parts - least loss of energy. I have read this many times, but perhaps it is wrong.