i completely follow what you are saying... i actually used paul’s zeros years ago when i was trying to run maggies driven by roger mojeski’s rm9 tube amp... you are right, when the amp really can’t handle the load, the autoformer poses no tradeoff... its autoformer or no music...
i was curious on the sonic degradation if used on an easy to drive speaker
also, i had never thought of using them with solid state amps! makes perfect sense, the autoformer provides any amp with greater electrical 'leverage' irrespective of amp type... ok i am going to try to find those zeros in my storage closet this weekend, maybe i still have em!