I recently did something quite similar to this
in Chicago. Our third night was 9 places in about 12 hours.
First, are you interested in a particular type of restaurant or cuisine? There are a ton of good ethnic restaurants in NYC obviously, not all of which are applicable if you are looking for places similar to yours.
Also, I think you will have to hit 2 or 3 neighborhoods if you want to go to 8 quality affordable places, especially if you want some variety. Which isn't that big of a deal. Travel time shouldn't be a problem if you plan a route properly.
I usually end up in the East Village and the LES. But I like cocktail bars/speakeasys and there is a good concentration of those in that area. Plus Matt is there and always worth a visit. You guys should visit him and there are some good places nearby you can hit as well.
I suggest making a list of every suggestion you get, finding them on google maps and "starring" them. Then you can zoom out and see all your starred items and see where they are concentrated and hit those areas. Places to add to your list are Momofuku Ssam Bar, Kuma Inn, The Breslin, Fette Sau, Fatty 'Cue/Crab, Ippudo, Takashi.