The Micro Amp costs a little more ($350), but I don't mind and felt it was worth it (I did the 30 day trial). The thing is built like a tank and it drove my HD-650 and K601/K702 much better than the Asgard could. Asgard won't even drive any 600 ohm headphones very well, but I didn't expect it to! Asgard is good though. HD-600 sounds amazing with it. Supposedly Schiit made the Asgard sound better with the K702, but I don't know. I didn't like that combination at all.
Also, as a nice bonus of the Micro Amp is you get morons trying to tell you you're driving all your headphones from a tiny portable amp!
I think for the Micro Amp you do pay a little more for the build quality, super small size and that it's made in the USA. This thing is half the size of the E9!!
I think the only headphones I don't like with it are the Sextett and DJ100 (amp overkill). Drives all my AKG headphones with ease (yes, and they sound good!).
One reason I got the Micro Amp is that I'm a huge fan of the Total Airhead. That was my first decent amp.
Someday I'll try the M-Stage and compare it to my Micro Amp. Who knows, I might like it even more.