Best 40 to 50k used speakers

The ATC 15 inch woofer produces some magic that is hard to change for anything else. I’ve tried and am trying :-) Then you have the transparent mids. Maybe the highs could be bettered but that's not so important for me. And the possibility to play at thundering levels...

@gosta which model ATC do you have ?I'm looking at model 50 and 100 depending on room size, the 150 is way too big for most people.I would drive them with Spectral monoblocks therefore i should pick the passive ones ?

https://www.marten.se/
Top quality gear worth looking into ... hardly anyone in the US has any on hand but EU should be a good possibility.
Ten years ago Audio Federation demoed different models Boulder, CO and RMAF.
Very nice ...

@thieliste I have the passive model 12 and 19 and the active 150 asl. I also have the Thiel 1.7, 2.2, 3.6, Ultima studio 2 and D& D 8c among others. Nothing I'm afraid really in my ears compares to the active 150. Might be because I listen from the bottom and up. Also sometimes at high spl's. So a very clearly defined bass/low mid is very important for me. And the 150 with the 15" woofer gives me that. Can't really say anything about passive 50's and 100's. Though I know the 110 is popular in studios. However, this is important, without digital amplitude and time correction it wouldn't be fun at all in my not too big room. I run Roon with (Acourate) convolution filters to a Matrix dac/pre.

@gosta I'm impressed at how you were able to fit a pair of 150s in your mid size listening room.You need some serious room treatment with these beasts.I'm gonna try to audition the 100 model as soon as possible.Cheers.