Known by locals as "BAM" this place produces some incredible shows, for instance Cate Blanchett in "A Streetcar Named Desire". I've seen some great things here and would highly recommend checking it out while you're in town.
Also, if you're really on a budget - I say just put some good walking shoes on and just walk from Soho to Time Square. It's a long ass walk, but you'll hit all that you need to see along the way (Little Italy, etc.) Pictures are the best souvenirs!
So you guessed it, the tallest building in the Western Hemisphere wins by a landslide for perfect date spot, even if you're going on 50 years. If things are getting too familiar just say to your partner, Hey Honey, want to step out on the ledge? You'll be safe. Glass boxes keep you safely inside.