The DC metro area suffers from surplus income - so the vast majority of shops sell higher end gear - be wary.

I can recommend one shop where the owner, main mechanic, and two sales people are all lifetime bicyclists who have seen and done it all over many years. They have a modest but wide selection, and will listen to you and work with you. Try to go mid day, earlier in the week (Tues-Thurs), don't show up on a Saturday when they're bombed with folks with flat tires, kids in tow, and cash in hand.

They're called Papillon Cycles in Arlington, off of Columbia Pike. Excellent customer service and knowledge. I ride >30 miles from home just to visit them at times.

There are other chains that price at the high end of retail, like Spokes, but they'll have a very full line of Treks and the like, plus a good selection of hybrid bikes, too. Revolution Cycles is largely overpriced. Performance bike has lower and house brands, but you can find some good values. Good luck.