Single ended Power amp recommendation

I thought I'd add that the speakers remind me a little of the Placette.---In that the Placette is small and light ---with a powerful wallop. The speakers are just like that.---They are light. Even the bass cabinet is light--but w/ a wallop. The top cabinet---the same thing.----My Montanas weighed 200 lbs--So I guess I used to think big bass--big cabinet. Even rap/ dance music sound great.---The R&D guys got all the right thing together.Altho the bass is there; it never lags or stands out---unless that is the way the music has been mixed--(Such as Dance music and rap--which I normally wouldn't even listen to.)

I had a pair of Quartettes for a short while before trading up to the older model of the J2001 (twin). The Quartettes do certain things that few speakers outside of big horn systems and old Western Electric 755-based systems can do. In particular, they hve a sense of energy, vibrancy and astonishing focus. This is a fun speaker that makes most others sound constipated by comparison.

But, they do have a somewhat lumpy bass response, light-weight upper bass and prominent midrange that can be problematic with orchestral music. These things can be addressed to some degree with proper matching equipment and set-up. The Quartettes are the most demanding speakers I know of in that respect. They are particularly sensitive to proper toe-in. Too little toe-in and some of that incredible focus is lost; too much and the stage collapses.
While they are rated at being something like 95-96 db efficient, they are apparently a very difficult load because so many amps I heard them with cannot control the woofer, making the response very uneven.

I know that Vincenzo, the designer, insists on tube amplification, but I've heard this speaker work quite well with the Hovland solid state amp.

Berning Siegfried.