I’m imagining 92db and greater then if I want to use SET down the line?Another factor that is equally important is that the speaker’s impedance should have relatively minimal variation as a function of frequency, or should be relatively high at all frequencies. Or both.
The Daedalus Ulysses that I use, and that a couple of others who have posted above use or have used (also with VAC Renaissance push-pull 300B amplifiers), have a 6 ohm impedance but combine an extraordinarily flat impedance curve with 97.5 db efficiency and high power handling capability. Which makes them exceptionally versatile with respect to amplifier selection. However I believe they cost upwards of $16K presently, if purchased new. Some of their smaller models, though, having a bit less efficiency and somewhat less deep bass extension, can be had new for something like half that amount.
The various Coincident models, one of which Charles uses, are also very versatile with respect to amplifier selection, and are certainly worth considering. As well as the relatively low priced (~$3K) Tekton Double Impact he mentioned, which in addition to being a remarkable bargain seems likely to be friendly to many SETs (especially those having relatively low output impedance), despite its 4 ohm nominal impedance. You may want to take a look at the current thread in which it is discussed extensively, and comments are provided by many ecstatic users:
https://forum.audiogon.com/discussions/tekton-double-impacts
Regards,
-- Al