That’s according to the Washington Business Journal, which reports that Madison Square Garden LP is looking for a space to open up a rather large new theater in the District. At least one source of the BizJo’s puts the size the potential venue at “6,000 seats or more, requiring up to 100,000 square feet,” which, just for comparison’s sake, would make it almost twice the size of DAR Constitution Hall. Steve Moore, executive director of…