Midtown Jewelers is my absolute go-to place for exquisite jewelry. Their selection and sense of style are the best I've seen in the Washington DC area. I've been using them for almost 10 years, and the results have been never fail.
I've purchased a wide range of items, from small and inexpensive to large and pricier pieces, and me and my wife have loved them all. Plus their pricing seems to be quite reasonable.
The owner, Bobby Singh and his staff, are always a pleasure to deal with, and are genuinely interested in what is best for you, as opposed to trying to push any particular piece.
I cannot recommend a jewelry store more than this one.