CharlieU, there is no question about MS600 being vastly improved over the MC200 both digital and analog out.
That's the common opinion and the reason I decided to pursue that option to improve the sound of my Sooloos system. The MC200 is pretty darn good on it's own, but it's a multipurpose unit. I don't see mods like power supplies making a noticeable difference to the sound. A different DAC, maybe. A dedicated endpoint strikes me as a better option than spending time and money tinkering. No disrespect meant towards those who do it as I'm guilty of tinkering with computers and networks.