That depends on the current draw from the amplifiers. Find out what fuses are on the amplifier, 2x20A? Something like that, at least that gives you a rough idea of what the amps maximum draw will be then. Then you need to find out how much current your amp puts out, (either in your manual or on the inside of the door panel. Then you'll also need to see how much current your cars accessories (lights, radio, wipers, A/C, defroster, etc.) draw from the battery. Always try and imgine the worst case scenario for this (driving at nigh in a snowstorm), that way you know if your system will handle it.
. But I read that the alternator on the 98+ models are 80 amps so hopefully mine is near this. The amplifiers have a 30A fuse and the other has a 60A fuse. I think I'll just get a cap, I'll probably be changing cars in a year so I don't want to spend money on the car itself, just the system .