I doubt that KVR cross-drilled rotors are bigger than stock. Simply because they cannot be. If they were bigger, they would not be able to clear the caliper mounts. Front brake calipers are two piston unit with both pistons on the inner side of the caliper. Rear caliper is a single piston unit.
the kvr x-drilled rotors are the same size as stock i believe. at least they look it. i purchased them a few weeks back along with the carbon semi-metallic brake pads. they are being installed today. the rotors looks SWEET!! you have the option to get them cadium-plated in either silver, gold or black which helps to cut down on them rusting out. my old stock rotors were a mess from the elements. all rusted up.
You know, you could always look into doing a full RX-7 brake conversion from a 3rd gen or some 2nd gens. They have larger brakes and 4 piston calipers, and those guys are always doing brake conversion so you can pick some up for cheap. I would do this myself....but no money=no conversion.