The SL 55 still sounded unrefined with the top up when I stepped hard
on the throttle. I don't mind the engine making a bit more noise when
you press hard but the raspiness had no redeeming sound qualities for
me. It just sounded like an old truck and I have a truck already.
I feel the same about the SL 500's engine. It's quite adequate and
since it is a GT style car, it's perfect - IMO you don't want a GT
pretending to be boy racer. They are opposites in refinement.