+1 on the Jamis Coda, as well as Proteus Bikes. I just bought a Jamis Coda (base model) at Proteus to commute from Rosslyn into the District.
In your price range, I would look at the Coda Comp. Steel frame and carbon fork. Both Proteus and City Bikes are Jamis dealers with very good reputations. In fact, both have employees that are also BFers. I got very nice emails from both of them while I was conducting my search for a commuter bike. Also, I know Proteus stocks Kona and Jamis, so you could look at the bike one of the other posters mentioned.