David Manley made his amps switchable to triode because, given a reasonable load, he thought they served the music better. If speakers sound better in tetrode than triode, I suggest that they would sound still better with a good solid state amplifier - like a CJ 2500A.
Speakers and amplifiers are literally made for each other. Most modern speaker designs are made assuming high current solid state amplifiers. High voltage devices like tubes do best when given loads that do not require gobs of current and steep filter curves. Electrostatics, on the other hand, are tough on solid state designs and, as they are high voltage devices, they were made for tubes.