Is the car still under the 3-yr/36k-mile warranty? If so, you can let the dealer replace it. If you get an aftermarket one, 1) the OEM amp will NOT be able to drive it, too little power, 2) will not fit properly, thus causing air leaks, and 3) possibly flex the rear deck due to its heavier weight. Are you sure it's the sub, and not the sub amp portion of the OEM amp?