closed headphones
ath-m50s (or m50x) $99-150
not known for a large soundstage however they have excellent sound, are built sturdy, have decent bass output and are of foldable design. i personally own a pair.
dt770 pro $150-180
these have a wider soundstage than the m50s but are not foldable. they come in 32, 80 and 250ohm models. the first two dont need an amp but the 3rd does. the higher the ohm the better the sound for these models (the 32/80 are most compareable to the m50s).
semi-open
dt880 $290
wider soundstage than the others and also better sound quality. they do leak some sound (semi open design) though.
you might want to listen to some of the sample clips on this website to get a good idea of how headphones sound in relation...