Here is a quote from Stereophile on the XA 30.5 test results:
" Pass Labs' XA30.5 is a Jekyll-and-Hyde amplifier. Ostensibly a 30Wpc class-A design, its measured performance reveals that it can actually deliver clipping-free peaks 6dB higher in power, while the fact that its distortion under those conditions is predominantly the subjectively innocuous third harmonic is commendable"
First, interesting that you'll quote Stereophile, who haven't actually
used the measurement machine you tout. But you seem deathly afraid of studying
actual Powercubes, as published by Peter Azcel in TAC. Why?
Remember, you started this thread to tout the Powercube. What makes you so afraid of learning what kinds of Powercube results actual existing amps have generated? Strikes me that there's a classic conflict between evidence-based science and simpleminded religious zealotry here.
But to the Stereophile data, all it really says is that Nelson Pass misrated the amp. It's actually a 130W/8Ω amp, not a 30W amp. And, incidentally, one that strays pretty far from the theoretical idea of doubling output as impedance is halved. Perhaps Papa Nelson's power-supply isn't as well-conceived as it looks to the eye of the untrained audiophool.
Given the source, one should probably assume the misrating was intentional so as to mislead consumers, not because of incompetence or inability to measure the correct output.
But nothing in that review negates my point that an amp with more power will play louder cleaner longer. Papa deciding to spec his amp with an incorrect number does not change anything.
Given the Stereophile measurements, it seems clear that an earlier Nelson Pass design, the Adcom GFA-5800, is simply a superior amp. It has a lot more power into all impedances, with equally negligible distortion. I'm not using my 5800 right now. It's in great shape. Want to buy it? I'll sell it for only 150% the MSRP of the XA30.5!

There are 100 watt amps out that don't perform as well.
I'll agree. The reason for that is that the manufacturer/marketer rated them honestly, rather than using the old 1990s car audio imbecile marketing gimmick of "underrating" that Papa is employing. ("Duudee, this 30W Rockford Fosgate Punch amp just flat POUNDS!" "Lanzar watts are a whole lot more powerful than PPI watts or a/d/s/ watts!!!!")
Yes, a 130W amp will play marginally louder than the typical 100W amp.
The above are "facts", so stop whining.
Not as the word "fact" is reasonably used by intelligent English speakers. They are, as I correctly pointed out, unsupported and conclusory assertions of your own opinion.
They work different, so guess what, they can and will sound different as result. You don’t need a spectrum analyzer to tell that, either.
That is again not a fact, but an unsupported cursory assertion of your opinion.
Words mean things. You would do well to stick to the actual accepted meanings of the words you use.
Furthermore, it is simply incorrect reasoning to go from the premise that things "work different" to the conclusion that therefore they must "act different."
Lastly, things often "work different" but "function exactly the same in every material way" in the real world.