I stumbled upon a store downtown around 18th and I. It's a pretty unassuming place, so I was surprised to see that it had a decent selection of stuff. If I'm remembering correctly, the store had both the '70 and '79 Darroze. The guy running the place was knowledgeable and eager to help. He was raving about the '79.
S&R Liquors. They have two bottles of Darroze right now, a '70 and '79 Cheateau de Gaube. Nice people and a nice selection of less expensive armagnacs including a few nice Casteredes.