my 96 disco stops very slowly so when i get the calipers from rovahfarm.com i was gonna do brakes all around and i noticed he had vented rotors, the cost is much more but im asking if it increase my braking distance that much more? also i noticed brake kits were sold seperatly, ive change many a brakes on chevys, fords, mazda, mitsubshi and never had to buy kits are they needed?