My experience with von Schubert wines goes back to the early 1980s when I bought some from vintages in the 1970s from a store in DC called Morris Miller. I then bought a bunch of 1983s, particularly Abtsberg Spatlesen that were absolutely fantastic. I had a change to go to a tasting led by Dr. Karl von Schubert of 1989s that were very eye opening. The 1989s were really fantastic up and down the line - esp. an Abtsberg Auslese #96. The 1990s were also fabulous. A great vintage for them. Bought for a few more years and then did not see their wines for a while. Have been buying again in the 2000s, esp. 2007 and 2015.
In DC, while a lot of stores carry a few German wines, generally there has only been one store at a time with a great German wine selection. When I first got to DC (1980), it was Morris Miller. Then, it was stores with David Schildknecht as wine buyer - first Rex (I still miss Rex), then Mayflower and finally Pearsons (during some of this time Eagle also had a great wine selection). More recently, the best German wine selection in the area by far that I know of has been MacArthur Beverages where the manager of the store is a German wine lover named Phil Bernstein.