Not enough power in my opinion
I had the M25 and the M55 and I was content with the cd player but the amp just didn't have enough power to play the summits properly. I realize that the M15 will play them better then the M25 because it doesn't have to power multiple things but I was not...
cd vs sacd
I listened to the regular cd and the sacd and I thought it was a pretty dramatic difference. Definitely worth grabbing on sacd in my opinion.