I decided on the HD280. Just got them yesterday, love them. even sound reproduction is right, these are the clearest headphones i've ever used, and the detail it displays especially in the mid/high end is exceptional, i can hear every little bit of guitar and vocals. Very clear lows, and never overpowering unless the music is mixed to be so. not an amazing sounding high end (cymbals) but I have only listened to mp3s and they tend to make cymbals sound terrible (yes I am the kind of person that hears a difference even on cheap headphones). I'll listen to some CDs or records tonight and I assume the high end will be at least somewhat crisp. The isolation on these is great, about on par with the etymotics. i have had someone trying to have a conversation with me from 3 feet away when i had these on with my ipod at about 1/4 volume.
for the price, these are incredible. I'm going to pick up a cheaper pair for school listening, these are huge and too expensive for me to bother. Maybe those $15 sennheisers will do the trick.
Also, reading some reviews apparently a headphone amp will do this a LOT of good. what should I look into, or could I just build a circuit myself?