If there are speakers that could use external amplification are Axiom towers. It seems one of the design goals that went into the towers like the M60 and M80 were power handling and the ability to play extremely clean at very high SPL levels and consume large amounts of power to fill large rooms.
It would be interesting to hear Ian's reasons for the design he chose. There are other advantages to using multiple drivers. You greatly reduce the excursion of each individual driver ensuring that they do not go beyond their design capabilities. That is a good way to reduce/eliminate distortion of various types.
