the calipers dont really see that much heat. you want to focus on the relationsip between the pad and the rotor. larger rotors, 2 piece design, cooling vanes, slots…all supposedly help with cooling. after upgrading to slotted rotors on my car, i cant really comment on cooling, because this is also the first aftermarket pad i have run since buying the car. yup thats right, 60k with many auto-x’s and highway pulls on the original, stock pads and rotors.
anyways, i decent pad if you arent already using one would be a great help. stainless lines imo are a waste on the street, only justifiable on the track, but i am sure this varies form car to car. brake ducts are great, but again i think they are a track benefit upgrade. larger rotors are the way to go. more surface area/more surface per rpm maens less heat. thats the way to go, but i fear that a caliper upgrade, or at least some adapting brackets are needed.
imo a good rotor and pad upgrade is the ebst way to go…and then a kit after that (larger rotors/more pots per corner) stainless lines and ducts are only for track use imo. good luck