I don't want to dampen your spirits, but just so you are aware, NYC audio shops are generally not very open to tire kickers. "Oh, I'm from out of town and I just want to hang out and listen for a few hours" doesn't fly very well in general. NYC can be a great city, but I'm just letting you know up front. Other than that, there are some very nice things to do here. If you can make a concert in Carnegie Hall, you will hear some of the best sound you ever heard, even from the cheapest seats. OTOH, Geffen Hall in Lincoln Center absolutely sucks. Dead and dry, IMO.
Enjoy yourself.