I'm using Koss KSC75 at the moment, which have amazing sound quality for their price. Seriously, they easily outperform Sennheisers (*cough*overrated*cough*) of three times the price. They're also very comfortable (once you adjust them to be just right at least, but luckily they're really easy to adjust). The only downside IMO is that they're open superaural headphones, which means that unless you turn the sound up real loud, ambient noise can be a bit of a problem (OTOH, this does make them ideal to wear outdoors, since they won't ruin your ability to hear anything but the music). Because of this I've been looking into getting some good closed circumaural ones, but the price difference is huge.