Pros: Good sound, forward and clear mids, controlled bass.
Cons: Requires a good seal for bass, coiled cable, mediocre sub-bass
Like tdockweiler, I'm a fan of forward mids and these definitely bring it. They are excellent for vocals in general, not just for male vocals. They're relatively neutral sounding with a tight, controlled bass that doesn't extend too low. They're far from being "extreme bass" DJ headphones and I wouldn't suggest them to someone who is a fan of real bass heavy electronic music -- I hardly noticed the subbass on these headphones, even when equalizing it up. It is present, but not thumping like I would want for that type of music. One issue I noticed was that if you didn't take the time to get a proper seal, it completely ruined the bass. The DJ 100s were very dependent on being placed correctly on the head to get any bass impact at all.
I loved the build quality on them -- they were comfortably portable and felt very rugged. Most of the design was very sturdy with the housing being metal. The pads, stock, were very shallow and uncomfortable for people with large ears, but were fine for someone like me. I could listen to them for hours without pain, but they were not particularly comfortable.
As for needing an amp, they're fine from a computer audio source, but require amping when coming from a portable source. A Fiio E5 or Fiio E6 is sufficient.
Retrospective: I take back the amp aspect. It really doesn't make much of a difference if you can hit a high enough volume.