Can't offer any advice on a shop as I've never been to NYC. As a heavy rider I can tell you from experience that bicycle wheels are much stronger than people give them credit to be. As a general rule more spokes and smaller circumference are a starting point of what features I'd be after in wheels. I'd make sure whatever bike I picked out had 32 spokes or more front and rear. I'd also avoid any kind of suspension. They come from the factory built for 160 lb riders and at your weight getting suspension to work like it's supposed to is expensive. I personally own a Kona Sutra LTD and a Surly Karate Monkey and I think either one of them would be a decent choice depending on what you mean by off road. Neither of those is a cheap bike but being that you're in NYC I'm assuming that "affordable" means you have the dough for a good bike. I'm judging that off of the fact that my friend who lives there pays more monthly in property taxes than I do for my mortgage and taxes combined, for essentially identical properties. I'd also consider a flat bar 650B to be pretty ideal for what you're talking about doing. A Jamis Sequel or a Kona Dr. Dew may might be a good choice for you. I'd prefer to ride one of them on the streets than a mountain bike.