It's possible to add more power amps to your PA, but you will have to basically assign them certain functions, and use a crossover. For instance, one amp could run the subs, another run your horns, and another for your mids. You would need the crossover to seperate the frequencies so you don't get bass in the tweets, yada yada yada.
So. If you throw a cat out of a car window, is it considered "kitty litter"?