I have both the HE-400 and the Mad Dog 3.2 Universal (with 1/4" cable) and I will probably be selling my HE-400s.
I was surprised by how much of an improvement the 3.2 are over the 3.0 version. The 3.2 revision pretty much fixes all the problems with the earlier versions. This makes the extreme clarity and transparency of the Mad Dog work well with most genres of music.
The two things missing are "air" and soundstage depth, and from the reports, the Alpha Dog fixes both of those, which is why I have pre-ordered the Alpha Dog (while keeping the Mad Dog 3.2).
The Mad Dog has less "ringing" and "smearing" that any headphones I have heard. It is like the difference between speakers in a room with a lot of hard surfaces (no carpeting) versus the sound of the same speakers in a well stuffed room with lots of drapes and carpeting...
I had the 3.0s and the 3.2s are on their way to me. Your post makes me think I'll be pretty happy with them (I did like the 3.0s, but I never had a proper amp for them).