In real terms probably very little difference, slightly different specs but the smaller hdcd looks a nice match for the MA astetically.
Just to say if you are not using the optical digital on the monitor audio you could in theory buy any inexpensive cd player that has an optical output and plug into the amp. This way you only use the player as a transport and the rather excellent monitor audio DAC as the music decoder. A cheap dvd player or bluray with optical out could do the same thing, though cd players are generally more user friendly