Before I upgraded my alternator, I was running my stereo, halogen headlights and driving lights on the tired old stock alternator.
You'd be looking at a pretty serious sound system if 100 amps doesn't do the trick.
Those 5700 watt amps will be measured as peak power - check the specs for RMS power, which is the actual DC power used to run the amp. If you can't find the RMS value, look at the amps fuse. The fuse amperage will be above the current that the amp uses.
For example, if you have a 30 amp fuse, the amp cannot use more than 30 amps - 30amps x 12volts = 360 watts.
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id be more worried about blowing the car apart with that sort of amp power..
It should be alright with the stock components, since the voltage determines the power - provide, say, a headlight with 12V, even if there is 100 amps on tap, the resistance of the lights will limit the current to about 5-6 amps.
Make sure you use the right gauge of wire with the new stuff you're putting in - go a bigger gauge if you can. Too small, and you can melt the wires You could say that a lot of the stock wiring is too small, but it's safe - just not efficient. You might want to check that all your stock wiring is in good order though - perhaps a second earth strap from the engine too.