IMO, you only really _need_ bigger rotors/calipers if you are going to be running sessions at the track. On the street, a better pad compound and stainless lines will do the job for most people.

Remember that increasing the unsprung weight (as bigger rotors/calipers generally does) can negatively affect handling. I'd say that a large percentage of people get the big stopping hardware cos it looks cool, not because they have a real need for it. My disk is bigger than your disk, if you will... ;)

juan