The STCC 2 cars (by the way, it's the 2010 season) would be a fantastic choice because you have varied competitive cars. The new cars are good (Scirocco, Cruze, 6-speed BMW, new Volvo), but you can also rely on the proven cars (Leon, Accord, Lacetti, 156, 5-speed BMW). A colourful and varied grid would be almost guaranteed. I only hope mostly other tracks than the standard STCC ones are used.
The Mini would be fantastic too. It's been a while since the RPM and RSC Mini Championships were run, but they offered great races back then.