Ralph, would the solid state McIntosh amplifiers with autoformers qualify as constant power sources? Their specs indicate the same power from any of the speakers taps, e.g., 2, 4, or 8 ohm, but with different levels for the output impedance. If so, that might explain the general tendency to pair these amplifiers with Martin Logan ESLs. My MC2200 model does seem to do quite well with my ML Aerius i.