The big 4 in DC area are:
Gifted Listener
Centreville, VA - Linn, Theil, Vienna Acoustic, etc.
SoundWorks
Kensington, MD - See above list
JS Audio
Bethesda, MD - Sonus Faber, Dynaudio, Bryston, Classe, etc.
Deja-Vu
McLean, VA - ? (never been there)
Gifted Listener
Centreville, VA - Linn, Theil, Vienna Acoustic, etc.
SoundWorks
Kensington, MD - See above list
JS Audio
Bethesda, MD - Sonus Faber, Dynaudio, Bryston, Classe, etc.
Deja-Vu
McLean, VA - ? (never been there)