Slightly better in treble balance. It sounds a bit more linear in treble rather than small peaks and valleys. The mid range also sounds more linear and there's a slightly different quality to it. It's hard to explain in words, but the mid range just sounds a little more clear even though I think it's a tiny bit lower in level than the HD600. Somebody else would have to give you the details on that one. In the bass, it's significantly more linear and has much better sub-bass presence. The bass also seems a bit cleaner. I'm not sure if this is because of decay or distortion, but the bass notes seem to be better separated on the Mad Dogs. Details in the bass are much easier to hear. At the same time, the bass doesn't get in the way of anything. It's there. It makes itself known. However, it isn't overbearing or anything. It's just a more linear sound, overall, and the mid range that you mentioned loving on the HD600 gets even better with the Mad Dog + Alpha Pad, IMO.
Edit: Sorry for taking a while to respond. High school interferes with a lot of stuff as far as time is concerned.
Edited by C.C.S. - 3/8/13 at 8:42pm