What is the best/fastest/cheapest way to get from Reagan Natl Airport (DCA) in Washington DC to Baltimore?

I fly to work in Baltimore (actually Owings Mills, MD) from Detroit My current flight will be discontinued soon, so I will be flying into Reagan Natl (DCA). What is the best/fastest/cheapest way to get from DCA to Baltimore during Monday rush hour? Thanks!

The MARC train from Union Station. Here's a link:

http://www.mtamaryland.com/services/marc/

It's not faster, but I believe if you take the metrobus express from BWI to Greenbelt it should cost less than Amtrak.