Starting a second system, need efficient speaker suggestions.

never heard these, but lots of reviews

Von Schweikert VR-4jr

Fyne Audio would work for you. I’ve not owned them but have auditioned them and they have all the attributes you are looking for. They are very efficient as well at something like 92db @8ohms. $4k might be difficult to find, maybe used, but they are outstanding. They are on my shortlist of speakers if I ever upgrade from my current speakers.  I’d also recommend Fritz speakers, which I do currently own.  They are easy to drive and have what you are looking for as well and are well within your price range.

REFERENCE MM DE CAPO BE II MONITOR

92 db efficiency

https://reference3a.com/products/mm-de-capo-be-monitor

+1 Reference 3a MM DE CAPO BE II MONITOR.  Fritz speakers would also be worth checking into. 

There’s a pair of used Volti speakers available at TMR.