Have you ever done any serious AB level matched comparisons between the XLS and any of your other well build class AB amps? With so many comments on such a very popular class D proamp, I am curious to know if you have any doubt that all else being equal (level matched, same high quality source etc..), there may be audible difference, however minor that may be.
No level matched quick switched double blind test, no. Nor anything to such an extent as I don't think its necessary after the various ways I've used them, as I have generally not done with other amps either. Not set up for such either as I have not felt any need to. I am not an ampliphile.
I've used them as external amps with three avrs with seamless results to my ears, initially replacing Carver M500s. Same for using as power amp with two of my 2ch pre-amps. At least 5 different pairs of speakers. Even used one without a pre-amp. I use three as sub amps at the moment, one is looking for work.
I just find them a great value and sound the same as a variety of other good quality amps....