I bought a set of CAD MH310 headphones a few months ago from Musicians Friend--they're normally $50 but were on sale for $30 for the stupid deal of the day. They isolate really well, have an extra long cord and the 1/8-to-1/4 plug adapter screws on so you're less likely to lose it. Sound quality is just right--the bass is there but not hyped, so they mimic my speaker cabs pretty closely. Very comfortable too.
http://www.musiciansfriend.com/pro-audio/cad-mh310-studio-headphones
http://www.musiciansfriend.com/pro-audio/cad-mh310-studio-headphones