Interesting challenge, though does "incl. differences in frequency reponse and within the power range appropriate to the amps" indicate he expects any amps in the test to be EQ'd to some notion of "flat" via some form of additional signal processing? Quite some caveat if so.
FWIW In a straight level-matched real-world test between the diverse types of amps audiophiles actually tend to use, e.g. class B solid state, class A solid state, push pull tube and SET I'd expect to hear differences. I have certainly seen Harbs used with all this and more, so excluding or nobbling any particular type rather voids the whole thing IMO.
I did not see any type of amplifier being excluded. Assuming audiophiles like amps with a full frequency response and have a volume control, you are in with a chance to get yourself a large freebie.
Which ones would you choose?