what speakers for 4k or less new or used

I really like my JM Lab 926s. They are efficient enough to never strain those amps and yet have bass that is about the best quality I have ever heard. They can be picky about associated equipment but, then again, any revealing speaker will be.

However, the easiest/best may be for you to visit the nearest dealer and see what they have since you aren't starting with any real direction. Good luck in your search. Arthur

Take a listen to the Revel Perfoma F32's or the Vienna Acoustics Bethoven Grands

Go for the Merlin VSM-M, tube harness, battery BAM. Can't go wrong with these.

I have owned many speakers including Merlin VSM's, Silverline Sonata's, Gallo Nuc Ref 3's, Talon Khorus xII's and many others. Some of these cost up to $10,000 - $18,000 new. However, the speaker I have enjoyed the most is the Usher 6381. Very, very formidable speaker. Build and sound quality are the best value I have heard in high end speakers. Cost is $3000 with a slight dealer discount new.
Does everything so right. Speakers are full range and always in control of the music. So intimate souding! Anyway, that is my 2 cents worth. I felt they outperformed the Merlin in every way and I love the Merlin VSM so much I owned it twice.

Check out the offerings from Green Mountain Audio. The sound of the Callisto is stunning.