Getting a bigger alternator could be quite expensive. If you have the cash why not.
But I would suggest making a tank circuit with an extra battery in your trunk just for your amps. Just do a

on the forums for "tank battery" or "tank circuit" (without the quotes). The optima battery is excellent for the tank circuit because it's a gel battery and it's much better then a regualr acid battery.
I have the same issue, I have 2 AMPS powering 2-10", 2 6X9's, 2-4" and 2 tweets. And I'm thinking of doing the tank circuit for my amps.
Hope this helps.