The MC501's are terrific amps. . The first thing I noticed compared to my MC252 was more bass, more 3D imaging. My MC252 sounded good but the imgaing was left, right and center. With my MC501's I sometimes hear imaging above my head and a sensation of layers ie a drummer playing behind a singer or guitar player. I am using them with SF Elipsa speakers and have not desire to change them. IF you buy the MC501's you will probably never want to replace them. I am very happy with mine.
