High eff speakers? Sonata III, Super III, OR ???

Greetings to all of you happy high eff speaker owners!

It’s important to be convinced. Finally, I am.

I’m looking to get into a pair of high eff speakers to run a as yet to be determined, 15 50 wpc, or so, SET amp (s).

In fact the amp may only be 8 or 10 wpc, I’m simply not sure which one. Maybe not 300b’s, as I am prone to busier and larger scale music at times. Sorry if that line shows my ignorance about low power amps.

My room is right at 14, by 20.75, by 8.6 gently sloped. They will sit on the short wall end.

I dig all sorts of music. My defaults are big band jazz & blues, vocalists. Contemporary jazz, acoustical and R&B… every now and then some gangsta bluegrass.

I’m looking to spend around $3K, give or take used or new, but probably used is the first thought.

Any suggestions are greatly appreciated as I have absolutely no clue here apart from the Silverline and Coincident I already mentioned… and Ive not heard either of them! So I'm wide open to any thoughts and especially experiences in this regard.

PS if your real world experience shows your choice (s) need a sub, please say so.