Have not heard either. I do own a Plinius SB-301 amp, which is Class A/B. Very happy with it: superb dynamics, excellent bass reproduction and control, wide and accurate soundstage to the point where you can isolate the players, midrange slightly warm, treble detailed but not at all in your face.
I would expect the Class A SA-103 to sound even better, and might have gone that route myself if I had more efficient speakers and a smaller room.