The thing about those is that the distortion in a modern amp of either kind is too small to be perceptible (again, unless you're trying to use an underpowered amp), and as far as #2 is concerned, yes it may be true, but it's irrelevant. Most speakers barely make it past 20k anyways, and most ears don't even get that far, so whether or not an amp can reproduce 200kHz accurately, or even 50k is completely irrelevant.

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