Ah, a Power Plant 12 is another animal. :)
It is basically an audio amplifier with a fixed output voltage.
The Benchmark wants up to 8A of power, which is almost exactly that power plant’s maximum continuous load. I agree with them. The PP 12 is too small, and that the power supply in the Benchmark is probably much better without it.
And while I hate to quote ASR, their video on the actual performance of the new generation of PP wasn't the best. I trust Benchmark's power supply capabilities a lot more than PS Audio here, but unless they have great surge protection built in, I'd use a Furman before any amplifier in my house. 15A though. :)