I like both the food and atmosphere of Fulton's. Definitely a more "adult" atmosphere for a night out for the two of you (although not necessarily a "quiet" atmosphere, if that is what you are looking for). The clam chowder was very good!
Are you wedded to DD? California Grill at the Contemporary and Victoria and Alberts at GF are also great "date night" locales!
Have a great trip!