I think Da Hua Market--623 H St NW in Chinatown--has changed ownership. Every time I have gone in the past few months, I've noticed that their snack selection has expanded.
They now have a really incredible selection of Japanese (and other asian) snacks, candies, crackers, cookies, pocky, etc. They have at least five different green tea candies, some of which I've never seen before. And at least 15 different types of pocky/pretz--I think a pocky-holic must be stocking the place.
It's definitely becoming quality snack food destination.
They also have a respectable frozen foods and and dumpling selection.