I'm having a hard time deciding on which Britax convertible carseat to get for my Acura TSX. My son isn't a big guy and certainly will not be tall. I'm considering the Diplomat. I'm afraid the Blvd will be to big. We have a Graco Snugride behind the passenger seat and that doesn't provide the passenger with much leg room. Does anyone have a TSX and a Britax? Any input would be greatly appreciated.