I’m leery of chains but Heidi’s Brooklyn Deli has been recommended to me. Although I cannot vouch for it personally, my curiosity is piqued.
From Lunch Encounter reader Gary:
If you want a delicious, hearty sandwich at a reasonable price, try Heidi’s Brooklyn Deli at 1725 Duke St. in Alexandria. Their fare offers a pretty close representation of casual deli dining in New York/Brooklyn. Their Italian submarine and chicken parm sandwiches will fill you up. For the daring try the Bronx Bomber, Hell’s Kitchen, or Cajun Turkey. Their bread is baked on the premisis every day. There is also a store on H St NW in DC.
The Lunch Encounter 
I did not know you were in Alex. I will go by today. I love the deli’s of Brooklyn…do you have a hot pastrami with melted cheese on rye?
s