80 series brakes?

I just called the blokes at parts to get some idea of cost of rotors and calipers. What I thought was the case was that when the 80 series went from 15 inch to 16 inch wheels that they also increased the diameter of the rotors and changed the calipers. Bloke in parts looked it up and told me that they were the same size all the way through the whole 80 series.

Does anyone know for sure what the facts are and where I might be able to track down some second hand in Brisbane/South Queensland. I have gone to 16 inch wheels recently and would like some extra stopping power.