closed headphones generally don't sound as good as open headphones.
Open headphones aren't as open as you'd think, i have the sennheiser 580's and you can just barely hear any outside noise when the headphones are off, and when the headphones are on to a moderate degree, you can't hear the phone next to you.
Basically, however, i think the sennheiser 580's and the sennheiser 600's (eBay for approx $120-200, depending on model) are probably the best sounding headphones anybody could ever own.
The Grado SR-60's and SR-80's (and above to the 325's) are very good headphones as well, but i never really caught on to their design much.
If you really care about audio quality and you just really NEED to have a pair of closed headphones, get the Sony MDR-V6's; i think u can look around and find them for under $60 pretty easily.
However, if you think that you MUST get closed headphones because you live in a dorm, forget it. I have a roommate and he can't really hear my Sennheiser's.