I just bought (today) my first Brand new car. 2003 Nissan Sentra seR. I love this car........except the factory sub. This car has the 7 speaker system, not the Rockford Fosgate System(I think). Anyway, I will be replacing the 8" sub because it souds like it's hitting the back deck. Can anyone recommend a decent free-air 8" sub that will actually sound good off the factory amp. Or should I just forget about it until the warranty runs out (3 years from now)?