I had an opportunity over the weekend to listen to a system powered by a pair of mono digital amps. They were Cherry Maraschino amps. They were driving a pair of Paradigm Persona F3 towers that retail for $10/pr. They use a beryllium tweeter & midrange, so not an apples to apples, but the beryllium tweeter should be very revealing. Perhaps not as revealing as the RAAL, I can't say. I could detect nothing that would indicate switching noise. The sound from those tiny cubes did not compute in my brain! Another guest and I both thought the sub was playing at first, but it was not. Those F3's can do some bass, and those digital cubes made them sing.

I'd be interested to hear the verdict on pairing digital amps with the Sierra-2 or Tower w/RAAL.