I have had good luck at Olsson's (I can never remember whether it is two l's, two s's or two n's).
And you can usually find good stuff at CD Cellar if you are willing to wade through the clearance section, the "slightly scratched" section (I've never had a problem with any disc there) and the regular section. They seem to have a line on promo copies of newer indie acts, often at $1.99. The Falls Church store is better than the one in Clarendon.