All I can go by is what I’ve owned. My favorite in the under $5000 used is the one I still have and have no reason to move on which is the Audio Hungary A50i class A.
You can pick up a used one around little over $3000. Never seems to stumble no matter how complex the music is. Has big tight bass but I do use 2 rel subs due to using book shelf speakers. I listen to mostly jazz.
I replaced a CJ cav45 s2 with the AH. The CJ was a very nice amp for jazz but the AH just grabs you with that fast solid bass and very realistic class A sound. I run kt120’s and 150’s with vintage preamp tubes and am very satisfied with the results with AH. No desire to move on so far.