While I haven't had a chance to hear the Ms on the A51, I did hook my stock LSi9s up to my buddy's A51 and the combo, while maybe not the end all be all of sound was rather impressive.
I am hardly an Emo basher. I have owned several and still have one residing in a closet as a backup. But the sound was not what I was looking for and as such, I moved on to other brands ultimately ending up with Adcom.
Eventually, I would love to be able to afford multiple brands of amps that can be swapped in/out and A/B comparisons can be made. But until then, I have to rely on others' experiences.