Many people think that if they need more volume, they need to pump up the power. While more power will surely increase volume, the power must grow exponentially to make a major difference in volume. The best way to increase your volume is to increase the number of speakers. Right now the woofers are getting up to 500W each. Your ears work by picking up the way air is moved.
More speakers move more air, period.
Ohm's law that is. Yeah, Ohm was a real person and he figured out the physics of electrical resistance and made up some cool equations to help us calculate impedance. For series wiring the equation is simple addition. For parallel, it isn't as easy. Now that you are all experts at calculating impedance, keep in mind to never load an amp down below its rated impedance.