There are three main ones IMHO. J&R, B&H and AC Gears. The former two probably have the best selection, but due to me working at the latter one, their headphone selection is getting better ;)
B&H probably has the best range though. Going from lowest of the low, all the way up to HD800s. J&R I know has a okish headphone wall, but I haven't been there in a while.
AC Gears just got in a few Sennheisers (specifically Momentums, HD598s and HD558s as well as several of their in ears). AC Gears also just got in for demo (before they get in the full shipment) HE-400s and RE-400s from HiFiMan.
Hopefully we'll get in Beyerdynamic soon.
hey - just got back from there. forgot to say Thanks!
I went to B&H and J&R but forgot the name of AC Gears... sorry about that. really wanted to try the RE-400 so that was a miss from me.
sad as it sounds but I had tried all the ones for demo at both J&R and B&H before.
well, was a nice visit. shame I didn't go earlier so I could have attended the meet!