sdl4 - unsound has a good handle on the factors. But there are even more complexities. Jim did a lot of work on that balancing act including the unusually low reactance of his early bass tunings. The phase angles are quite low and at higher impedance where the amp can handle it better. But to your question: not quite even in today's world.
This afternoon I drove the system up to flickering clipping lights on the stereo AHB with Chris Thile - Edgar Meyers 'Bass & Mandolin' album. The calibrated Benchmark preamp clipped the AHB @ 2dB lower with the 20Hz equalized signal compared with straight-wire / no equalizer. I got similar results with Patty Larkin 'Strangers' World' cuts which are mixed for 'impressive' bass impact.
Jim's intent was to get that extreme and excellent bass extension without significant penalty. And it worked in the 1980s. Remember that vinyl was still the standard which is bass limited by cartridge tracking ability. But the landscape changed not only with digital, but with showcase albums from David Wilson and others which were engineered for 'unbelievable' bass. The Watt/Puppy could handle the real cannons in his recording of the 1812 Overture, but Thiel's model 3 would bottom out because they actually reproduced those deep frequencies. Similarly digital bass could go deeper with more power, and was therefore no longer predictable. So, even though Jim took great care, and his parameters balanced out to require little to no more power in the bass than that required by midrange transients, when the signal landscape changed, the elegance of his solution became practically less safe.
