Take a look at Sennheiser HD595 for a slightly laid back (relative to F107plus5's suggestions) smooth sound. When my uncle heard mine (when I still had one), his only comment was that it sounded like a stereo system. Mine was connected to a portable amp, but the HD595 sounds good without one. I think you can buy a new one for $200 or less.
If you like a more bassier sound, then take a look at the Audio Technica A900 which can also be bought for a little under $200.
But my strongest advice is for you to audition headphones. Headphone listening is a strongly personal and subjective experience so trust your own ears. If there is no local store with demo headphones, then go to Head-Fi meets. Better yet, register for the Head-Fi International Meet which is only a month away in San Jose.