As I recall Thiel was using Threshold ss amps to voice their speakers when these came out. I used a Class A Threshold on mine for several years. Sounded better than others I tried at the time. I never tried tubes, but I would imagine if you did you be talking about large powerful PP ones and they might just sound pretty good if they could handle the bass. I use just such amps with my present dynamic speakers to my great delight.
