I've done carefully level matched single blind comparisons...nobody could identify one amp from the other. That was using conventional amps that were linear, with low distortion, low output impedance (despite what the Doc says, virtually all amps, or at least conventional ss a/b types, have output impedance of a tiny fraction of an ohm), and kept well within their safe operating limits. When those qualifiers are violated is when audible differences manifest themselves.
They applied some cost cutting that inappropriately applied conventional thinking to Walker's innovative design. The old ones that were made in England perform as intended. The new company's interest seems more business oriented: milk the legacy while watering down the product. We've seen that before.
Oh, Peter Aczel's power cube measurements would sffice.
I think this whole topic indicates where, historically, from a pure performance point of view, divorcing amplification from speakers as products was a mistake. Commercially it wasn't a mistake, to be sure, but it sheds light on the reality that what should really be a design choice of engineers is put onto the consumer. The dominance of passive speakers has consumers doing this engineering guesswork instead, mired in confusion that spawns threads such as these.
