to the OP, there is nothing wrong with RF or Kicker, its just that better values can be had. Honestly, I think that Mtx is just as good when it comes to the mainstream brands, as is Alpine. They are all pretty close. And all in similar price range. Between those, Id prefer Fosgate.
If you are on a budget, you might want to look at Maxxsonics products (MBQ, Hifonics, Crunch, Autotek) and perhaps companies like Phoenix Gold. I know they have a line of subs that have been getting good mention lately for budget builds on this site.
People are gonna act like dicks to you initially on here, but as long as you dont lie (doing a 157 off 2500rms in your "custom box") and dont act like you know everything, there will be plenty of people with advice. But make sure you listen, and ask questions to clarify if you need to. But also, do research yourself, most people dont wanna "hold your hand" through everything....
So first, come back with your budget, car type, what you would like, and if you want sound quality, or SPL