Have you checked out the OZ Racing rims on the Mazda Mazdaspeed3 in the Continental Tire Challenge? The O.Z. Alleggerita HLT is used on the cars for the road racing series. They are a complete street wheel but they only weigh 15.6 lbs in a 17x8 wheel. Unlike other racing series, these cars are dedicated race cars but they are running street wheels that anybody can buy and use on their own car. Lightweight wheels will improve the car's performance by reducing unsprung weight.
Even though the wheels are light they are also still very strong. Sounds like a win-win.