spend a little or a lot
the difference in quality between cans $50au and $150au
is that great but diff between $150au and $300au is huge
read the freq specs
listen to some different pieces music you know through them
one track with accoustic guitars (will be able to pick how well it handles transients by listening to pick noise on the strings amongst other things)
one track with female vocals
one classical track
one full spectrum dance track (dnb works perfectly)
listen to other ppl advice... but in the end let your
own ears make the decision..
mine are budget audio-technica ath-m40fs. semi-closed. good for the price i paid (80€ from thomann) but the midrange is colored and it pumps the sub too much. dont forget to listen with other than headphones too from time to time, gives you perspective and is dead important when your cans are new, so you get familiar with their sound.