In NYC, there are basically 2 streets with tons of watch stores.
For the high end stuff at the big well known places, the Tourneau on 57th St. between Madison and 5th Avenue is I believe their biggest branch. In the very immediate area of that store are several other similar competitors, of those the most well known are Kenjo (this one's only in NYC) and Wempe, which has a bunch of German stores but not very many elsewhere. All 3 and several brand stores (AP store, Omega store etc.) are in very close proximity and you can travel to one and walk to each additional location in 5-10 minutes easily. The problem with most of these locations is that you will find it tough to get a really good deal, they have enough tourists pumping them money that they won't go much lower than retail (if at all).
The interesting and much cheaper alternative is the jewelry district. This is 47th St. between 5th and 6th avenues, and this is a much better location in some ways and much worse in others. You won't find any SUPER high end stuff, but what you do find is amazing deals on the common brands (not cheap though, Rolex/Breitling/Panerai), and a ton of used stuff at great prices. And unlike the chains on 57th, you can and should haggle at any store here.
Sorta unique is my favorite watch location in the city, and very well worth it if you're into vintage stuff. Aaron Faber's (
http://www.aaronfaber.com/) is amazing for old stuff, but has zero items that aren't preowned. Small store, but the place is like a museum.