How about the bar at Equinox? Great food and you can get a few nice glasses of wine or a bottle.
If you are looking for something a little more modern and moderate priced, I would suggest PS7. Their lounge has a great menu with fun appetizers like mini tuna tartar sliders and a homemade mini half smoke platter. Really creative drinks as well. Washingtonian just named their bartender best in the city.
Another option around Chinatown/Penn Quarter would be Jaleo or Zola.
For something a little more pricey but totally worth is is Taberna del Alberdero. You can a few plates of tapas and a delicious glass of wine. I highy recommend the croquettes...the best way to celebrate ANYTHING!!