I would be curious about this too. I have heard that Alan Furman is good but I have not bought from them. They have online but also a store in the MD/DC area.
Princess Jewelers in Vienna, VA. http://www.theprincessjewelers.com/ My office is 2 blocks down from them. I haven't had a chance to run over there yet, but they seem pretty nice, from what I can see when I drive by everyday.