There isn't time to read all of this thread, so my apologies if it's already covered the Red Dragon S500, but I've had that for almost two years and am really pleased with it. Sound is detailed, balanced across the frequency range, bass is deep and articulated, mid-range is clear, treble is also clear and realistic though I sometimes think it might show a little more sparkle. Certainly it's well ahead of the Class AB monos I had previously, and they'd been well recommended.
The main partnering equipment is an Esoteric X05 SACD player, Townshend Allegri preamp, and B&W 804S speakers.
I don't doubt that there may be better Class D power amps. Some will be better because of their design and the quality of their components. It's also possible that some Class D modules are better than others. Living in Britain I don't get much opportunity to compare the sound of different systems. I did hear one of the first NORD NC500 power amps (it's only an hour's drive to where they are made), but the demo wasn't very successful from my point of view - mainly to do with the circumstances and not necessarily a criticism of the amp itself. Buying the Red Dragon was something of a risk because although I could return it within 45 days, I wouldn't get the import duty back and there's be expensive carriage costs. But it's been highly successful and I'd probably have to pay a lot more to get something that performs significantly better; though in five years' time, perhaps, when things have moved on a lot, better quality may be available more cheaply.