I don't understand why you don't think you can push your car. Bmw might be one of the only companies that makes a car that is great on the street and can take a hard thrashing on a track. Maybe exempt the 330 because of the damper. But yeah, a bmw will handle a thrashing stock better than just about any other affordable stock car.
If you need something faster, I understand. If you want something lighter, I definitely understand and recommend a miata or e30. But if you're serious in saying you don't think it's capable then you need to rethink.