The only Dinan dealer I know if in that area is Sterling. I'm not sure if Towson or Passport are. Personally, I couldn't stand Sterling when I was there and from what I've heard, their attitude hasn't improved much. A very "my shite don't stink cause we're the largest dealer on the east coast" attitude. Noses very high in the air and all that jazz.

As far as discounts on Dinan, call Dinan themself, or give Sterling a call and BMWCCA to see what's up. Again, just personal preference, I think you pay for the name Dinan and don't see as much performance gains as you could with other vendors. Just food for thought.