Whats a good dress store for prom?

i live in northern va area im willing to go a little out the way though. I have been everywhere so far (including tysons, tysons II, georgetown, pentagon mall, mae dress boutique, ann's dress boutique) i can't find anything at all and if i do fall in love with a dress there about 2000 -3000 dollars. and im not spending that kinda money on a dress for one night. I'm willing to spend about 900 on a dress. PLEASE HELLLPPPPP!