Metro, which has locations on UWS at 88th St and on 14th St., as well as their other stores, Westside, Midtown and Canal Street, also carry Giant. For my money, you can't beat Toga, though. I live relatively close to their Upper Nyack store and get all my service done there, even though I didn't originally buy from there.
If you want to take the train up to Mt. Kisco, I just got my Giant Defy 2 at Bicycle World, and they do free fittings before you get the bike so you can be matched to the correct bike (it is 50 dollars down but refunded if the bike is bought.)