No way are you getting that deal. The dealer is gonna lose money and last I heard dealerships are usually in it to make money. The economy sucks but it isn't that bad!! The best you can hope for is invoice and what you are wishing for is a few hundred below invoice. The dealers themselves don't get free mats.
I'd take the 500 and call it a day. You're already paying 40k for a car, 500 more isn't gonna kill you and probably isn't worth the time and effort fighting over.
You can also look at ordering a BMW online too since I heard you can get it for invoice without much negotiation. Forgot the site name though. I believe the dealership is in Baltimore, don't know how far that is from you though.