A 420 would be my recommendation, with the roller barrel upgrade for the noise and throttle response. I have an older sigma 150 which has similar performance to a 310 and sounds even better due to having throttle bodies. The engine is the best thing about the car - revvy and noisy with lightning throttle response. However you do have to work the engine hard to make progress. I don't mind that but have never had a torquey car in the past. On track, instructors have mentioned I could do with more power and it is frustrating to be slow on the straights and not having the torque to steer using the throttle. I once drove a 420 on the road and was surprised by how much quicker it was.