PS - The latest PS Audio's limits are known, like you say they are essentially amplifiers, but the noise on the output is unexpectedly high, even given Class D. Modern audio Class D amps are much better when driving sppeakers.
Perhaps a future version of PS Audio's regenerators will use spread-spectrum Class D to minimize that.
Personally I'd rather use mechanically switched voltage regulators. Even more efficient, no amplifier switching noise and all the current my wall can provide. The one negative is the mechanical noises. The switching as well as the occasional mechanical hum.