what else will i have to upgrade?

Friends don't let friends buy Sony. (or Audiobahn) or trash in general that is normally sold at flea markets. I would also look to a single larger amp to drive both subs instead of the one per sub idea. This is to simplify both the installation and setup of the system. Imagine if your car had an engine for both sets of wheels for example. Keep it simple, use the one amp for both subs approach. You generally spend less on wiring, install time and save on weight and real estate in the trunk. Top Secret, I can tell you but then my wife will kill me.

This is what ive decided. Im going to buy 2 12 subs (2 ohm) and wire them series/parrallel. Im looking at approx 300 rms watts with a mono amp to push them both. Pretty simple thank to all the suggestions and tips. Im going to install that first, and then see if the wiring needs upgraded related to the alternator. any sugggestions on the subs?

what do you think of the Alpine SWS-1222D ?