I need some sub advice

Look, you're 16, and your not competing with friends an whose got the loudest bump.  So I'm assuming you want to play music that seriously sounds good.  Now with a modest budget...What are you starting out with?  Just what the car has from factory?  You will also need a pair of coaxials to replace the front door speakers.  You can power the whole system with one amp, but make it a 4-channel:  half the power at 4 ohms to the coaxials, the other half of the power at 2 ohms to the sub.

If all you get are subs, you're going to get a loud bump, but its going to sound like sh!!t.

The Audiobahn box is model number ABP12, is that still a good box? Also, willl that one 12" really hit harder than the 2 12s? I want people to hear me coming, so I want something that will get good bass outside of the car, as well as inside.  My friend recently purchased that Pyramid amp for his car. Its hooked up to 2 Memphis 12's. It pumps good inside the car, but not much bass gets out. It could be becasue he has  Lincoln Towncar, which has quite a bit of sound deadning.  Also, is MA Audio a good name.? I found some reasonably priced subs from them.