Power Dinner Spot
A couple of places to check out would be J&G Steakhouse (the steak is excellent, but so are the other items on the menu, especially seafood), Vidalia (excellent gourmet Southern cuisine), Acadiana (delicious Cajun/New Orleans food), and Equinox (local, seasonal cuisine. The President and First Lady dine here often!).
None of these places are necessarily cheap but they are all excellent.
Lots of good suggestions - I would add:
If Congress is in session you should hit Capitol Grill on a Tuesday or Wednesday to watch "Republicans Gone Wild!" (At least have a couple of Martinis at the bar . . .its the best show in town! )