You can get yourself in the muck of all that technical stuff for nothing. I gave my $.02 on the Studio and recording forum where you posted the same thread. General Rule, have more watts of power than you need. Better on your speakers if you have more than enough power than if you under power and turn it up too far. That's why I recommended the equipment I did in the other forum. The subs I mentioned had a built in crossover.

I still don't understand everything there is to know about Ohms and that kind of stuff. I have a friend who owns a music store who I trust. That's what I would do if I were you. Just ask someone who knows, and then come back and ask some of us to make sure you aren't getting ripped off.

I play keyboards, but I don't exactly know all the science that goes into building one. Same with PA gear, I wouldn't let the science get in your way too much.