[mikegett]

Wattage has little to do with it. The main factor is how many amps are being pulled at a continuous time. You will hear from many people that because they have a 1110 watt (rms) amp they are using 1110 watts. This is seldomly the case. Your wattage varies as the volume changes. In many cases these 1110 watt systems are only seeing about 300 watts. You may find it hard to believe, but your four channel driving the main speakers will probably draw a larger continuous amperage than the sub amp. A sub draws wattage in bursts while the mids are continuous. Various factors will change this for each individual. What type of music, how loud, speaker efficiency, gain setting, sub enclosure, and even wiring. In short. Your car and system is unique. The only way to know is testing your amperage draw. You can either take your car to autozone or buy a tester. Place the tester between your altenator and battery. First test your car with the radio off, car running, and ac on. This is the cars current draw. Next, turn on the radio and increase it to the loudest setting you might listen to. This will be your altenators RMS draw. As long as you keep the rms 20 percent under the altenator rating you should be fine. For example. If the altenator is rated for 100 amps. You should not pull any more than 80 amps rms without risking premature failure. I believe our altenators are rated for 145. This would give you 116 amps.