There is only about 1% of 500kHz switching noise on the speaker cable, and that is absolutely irrelevant. Placing an ear next to tweeter proves only that people cannot hear 500kHz (almost complete silence). Modulating 500kHz by the tweeter would require its membrane to move at this frequency - not possible. There is no sizzle of any kind in my class D amp. If anything, class D amps are reviewed as "dark sounding". Yes, higher bandwidth would be always nice, but 65kHz -3dB sounds fine to me (some class D amps go twice higher).