Check out Sonist Speakers. I have heard the Sonist Concerto 2 at the RMAF a few years back. Using DeHavilland SE tube amps. Stunning sound.
Good monitor speakers for 300B amps.
That is it. Let me know what you think, what you have heard, and what you have used in your system, and don't be afraid to offer an opinion even if you have absolutely no knowledge about the subject.