The box resonance peak is where it is. How does the Power Paradigm amplifier move that peak to a lower frequency?
If the resistance in the bass region goes up (due to a box resonance) then the current into that higher resistance goes down. the voltage must go up to keep constant power. Where does the bass extension come from?
This is a matter of design. The peak exists as a relationship of the driver and the box. Change the relationship, change the peak. The bass extension comes from designing the box so the peak occurs at or below the cutoff of the driver, in such a way that the peak maintains the bandwidth. Not hard to do if you understand speaker design.
I believe that a traditional SS amp (one that was not designed for an ESL in mind) will likely sound mediocre 'cuz of the high capacitance load that will tend to make that amp oscillate & eventually fail. OTOH, if a SS amp is designed with an ESL in mind (& a few names come to mind that are being used successfully with ESLs & planars) then these SS amps will be effective.
Belief and reality are usually two different things. In this case I invite you to do the math. How much power will an ideal 400 watt SS amp make into 30 ohms and into 3 ohms? If you answer 'about 100 watts and about 900 watts' then you have some grasp of the problem.
to be fair, when the SPL get's really high, my ears hurt. So what's the point of that exercise?? ;>')
If that happens with less than 105 db, then its an indication that the system has some sort of odd ordered harmonic generation associated with its operation. A sound pressure level meter might be handy to sort out the actual volume level.