For what it's worth...
I presently own Mad Dog Alphas, ZMFs, and Sony MA-900s. I power all of these using a Parasound speaker amp which is capable of 7.5 Watts into 50 Ohms. That's watts, not milliwats. Needless to say, I never run it at full power!
In any case, my clear preference among these three is the ZMF. For my ears, the ZMFs have the most natural sound with the greatest detail and instrument separation. ZMF has slightly greater treble extension than my pair of MD-Alphas. ZMF also has a more neutral mid-bass... does not add artificial huskiness to male voice. I don't know why, but the MD-Alphas always seem more congested in the mid-range than the ZMFs to me. Both have excellent bass. The ZMFs use the Brainwavz ear cushions HM-5, which I find more comfortable for long term listening than the MD-Alpha Alpha Pads.
For me the ZMFs have excellent soundstage as well. About the same as the MA-900, and better than the MD-Alphs.
The MA-900s are great, but to me are in a totally different category. They just sound slightly more like speakers than actual musical instruments, compared to the other two. I like their lightness very much, although I don't find their standard ear cushions very comfortable. I haven't found a suitable substitute, though. I usually use the MA-900s for movie sound.
I am on Dan's waiting list for the MD for Alpha Dog trade back, but haven't received my go ahead yet. Actually, I'm surprised that the reviews on the Alpha Dog thread aren't the raves that I expected after Jude's initial review.
Hope this helps someone.
Edited by jdg711 - 11/10/13 at 1:46pm