DO NOT get the 245/45s because the tall sidewall looks fugly. I had these at one time and the handling was not as precise either, almost truck-like. This was right before I got my 18s, so the driving feel went from dump truck to sports car instantly. The 245/40 would be much sleeker and also handle better.
I would have to say 18s are the best overall for this car though. Ride in a Supra with 245/40-18 front and 285/30-18 or 285/35-18 rear and you can really feel the difference.