Hi Matt,
Did you buy the Sennheiser HD25 SP's? I've had a pair for a few years now and am very happy with them. Sometimes there's contact problems where the cable plugs into the headphones, but other than that, no problems.
The sound isolation is very good. Don't need active noise cancellation
not much soundstage, and the 'phones sound closed. but i guess that's the way it's designed.
take a look at a detailed review here:
http://www6.head-fi.org/forums/showthread.php?t=72883
good luck!