its output impedance is so high that only speaker has reasonable punch driven by those type of otl amps is eletrostatic speaker. Furthermore ,even after extentive mod, atmaphere amps longtail differential driver stage is too weak (guess which tube number is the dtiver tube :)).This statement is outright false and is clearly trolling. Its also quite clear that the gentleman has no idea what he is talking about as the circuit he refers to does not exist in the amp.
As an example the most common speaker used with the M-60 was for many years the Merlin VSM, which is a 6 ohm loudspeaker.