Just upgraded from Emotiva UPA-1s to a Buckeye 2-channel Purifi ET400A. Although the improvement in sound quality was not as significant as the one I experienced after upgrading from Sierra-1s to 2EXv2, everything sounds smoother and the sound stage seems deeper. It is definitely a better match for the 2EXv2 in that I am able to listen louder and for longer periods of time. I am very pleased.