HELP!! I KNOW NOTHING ABOUT CAR AUDIO

Careful not to overdo it here. If I read your posts right, you have a Pioneer 3200 double din that feeds the stock speakers, right? If so, you have only about 15watts rms going to those speakers. If you pump 500, 1000, 1500 watts to a sub, or multi-sub setup, then your door speakers are going to be underpowered and you will be way out of balance between the sub(s) and the rest of the sound (doors).

If you plan on keeping the stock speakers powered by the 3200, then you should not need more than 200-300W to a single sub. Now, if you want the too-much-slam sound, with no mids-highs, then power the crap out of it. If you buy too much power for the sub and do want a balanced sound, you'll be turning the gains down on the sub amp and basically paying a bunch of money for power that you can't use.

For example, my setup is my HU's pre-amp outputs powering a single 4 channel amp with 2 channels feeding a set of Focal components up front, and the back amp channels are bridged to a single 10" Arc Audio sub. The amp is rated at about 75W per channel to the front comps and about 200W to the bridged rear channels. MORE than enough sound and thump for me.

I think you'll be more than surprised at the amount of sound you can get from a couple hundred watts to a single sub.