Wonderful headphones, lots of bass, and very detailed, very deep.
I have mine EQ'D, so I can get more out of it, and its absolutely amazing IMO.
They don't have a good soundstage, but it sounds like thats not what you are concerned about.
They can be had for 90-150 bucks, depending on how hard you look. Your best bet is price matching them at a guitar center if you can.
An amp will make them sound better and you'll get a bit more out of em, but its not 100% necessary to enjoy them.
Another viable option is the sony mdr-v6, though the Audiotechnica's would probably be better.