I'm pretty sure there was only 1 Panoz GT1 streetcar, just enough to homologate it for FIA.
I think you're right, Danny owns the street car business, and Don owns the Chateau, the winery, Elan Motorsports Technologies, Panoz MotorSports, ALMS, the Panoz Race School, etc.
FYI, the Esperante looks so much nicer in person, and there are more than 15 around...I saw at least that many, and probibly more when I went thru the factory this summer. Gotta love a car that Danny christens with donuts in the parking lot, before its delivered!