Well, after a while I finally decided to go for those Quatros and did so.
Got them a week ago and only now got home to update the battery and tune the HP filters and get a dedicated listen.
Unfortunately I discovered that midwoofer on one of the speakers produces distorted sound (especially audible on piano). I did all the fiddling with changing the wires, amps, sources, powering the speaker off, etc, but the middle speaker (right below the tweeter) sounds distorted no matter what I do. The other speaker sounds better.
The seller tells me that all was good with the speakers when he was listening to them last. Also, a week passed since I received them...
So. Has anyone had experience of this sort? What can be wrong with them?