Why slotted? Have you given this any thought? They won't stop you faster. They will eat your pads faster. They cost more for less performance. What's the justification? You would benefit more from a good quality solid rotor if you really need them. For the price difference you can buy some really good performance pads and come out way ahead.
FYI, Porterfield R4S's are a fairly aggressive pad and have a higher price. Yes, its their street pad but a high performance one as well. As such, they need a little heat and won't bite quite as good the first time they're used or until they warm up. They are a very good pad for a multi use car such as street, light lapping and autocross use. They are also one of the few pads that has a matching rear shoe if you have drums on the rear. The Hawk HPS or Mintex AF might be a better option if the intended use is primarily for the street. Both of these pads work well for autocross as well. We currently have the Centric/Mintex combo on our car and like it alot. You'd be happy with the Brembos as well.