Amounts of diapers/wipes?

We'll be cloth diapering twins, and we're starting to stock up baby stuff now, since who knows when they'll come. How many diapers & wipes do I need for 2 newborns, instead of one. I read somewhere 600 for the first year, in total, but that didn't break it down by size. We'll only be using the pre-folds for the newborn stage, and then move on to a mix of pre-folds and contours for the rest of the diapering times. Also, can I use old, sewn-into-a-square cloth for wipes, or do we need to exclusively buy wipes too?