Well I don't know too much about the Mad Dogs. Although, I simply want a balanced headphone with better than usual mids, since I was spoiled with those of the UE6000, and detailed highs . I don't care too much about bass, as long as it is not nonexistent. I am looking for something under $400 ..
Hmm, well people do sing praises about the "liquid ortho mids" on both the Mad Dogs and the HE400. From what I've heard, the bass on the HE400 has a bit more slam, and the treble is a bit hotter. The MD is a bit more laid back in the treble, but IMO it retains a great amount of detail, despite not being forward. Also, there's quite a dip in the upper mids of the HE400s if I'm not mistaken by these graphs:http://www.innerfidelity.com/images/HiFiMANHE400.pdf