Not any A/B-ing, yet, but off memory I can definitely tell the MDs and the K712s both scale better with the extra power... expecially the MDs. It gives both headphones more body to their sound signatures and surprisingly has an openness to it as well. Not as large as the M-Stage, I think, but definitely larger than the iCAN on default.
I will do some definite A/B-ing with the M-Stage on Thursday and over the weekend... so I'll be back with more impressions. I'm really liking what I'm hearing, so far.
Ironically, the reason I got this amp was for the MDs... which I just sold to fund something else. It looks like I'll be keeping it, however, because I really like what it's doing to the K712 enough to justify it. I can only hope it has the same effect on what's coming next...
I still think there's way too much overlap between an M-stage and an Asgard to own both, but I guess your reasoning is that you need an amp in two different spots and can't move it?