I built both of those amps from kits back in the early 1980's, and aside from the exterior difference in cosmetics, there were a few changes to the internal components. As I recall (and the memory dims after 20 years), the DH-220 had a slightly larger transformer, somewhat larger filter capacitors, and better quality bypass capacitors than the original DH-200. I am less certain about whether there was a quality upgrade to the MOSFET output transistors, although I vaguely remember reading in an article that this was the case. Based on my own recollection, Plato is correct that the DH-220 was a better sounding amp than its predecessor, but the differences aren't dramatic and will not be particularly noticeable in the lower-priced systems likely to be used with either of these amps.
