Can a 2g alternator handle two amps?

[clean2g]

I have a 97 GSX and I'm trying to add a sub to my system. I've already added an aftermarket head unit and the interior speakers are still using the factory amp. I was wondering if there is going to be power issues with the alternator and battery if I add a "1000" watt amp (It's not a true 1000 watt amp.. probably actually only 400 watts). Anyone know what the power rating is on the stock alternator for the 2g's? If you have any suggestions I'd love to hear them, thanks.