sub question
 

So i have two ideas not sure of whats easier... 1. But another stock pioneer sub and put it on the otherside of my trunk. A. would i need to buy another amp? or could it run of the one that the other ones running off of? B. is it possible to mount it on the otherside?
2. To buy a 12" polk sub and put it in. A. can you hook it up to the stock subs wires? B. Can it run off the stock amp? or will i need a new one? B2. if i need a new amp can it use the wires the stock ones using now?

Easiest way to get this done,
Get an LOC (line outpout converter)
Get a new sub/box (the polk one your talking about will do in this case)
Get an amp that matches the power that the sub needs.
disconnect the stock sub
wire in your new sub
(not using the stock wires)

I would just get a new sub and amp. It will be a big difference in performance. Here's what I did:
https://www.cobaltss.net/gallery/fil...3/pana0302.jpg

I just used the factory sub as a template and built off of that.

A little MDF and fiberglass and some elbow grease

https://www.cobaltss.net/gallery/fil...3/pana0293.jpg
https://www.cobaltss.net/gallery/fil...3/pana0296.jpg

If you aren't comfortable doing it yourself, any good shop can do this. Good luck

Is that all wood, or is there glass in there?

One more question, is that the template for the Cobalts back deck lid hanging on the wall behind you?

https://www.cobaltss.net/gallery/fil...3/pana0285.jpg

https://www.cobaltss.net/gallery/fil...3/pana0286.jpg

.75" MDF front and back w/smaller pieces cut for bracing

https://www.cobaltss.net/gallery/fil...3/pana0287.jpg

https://www.cobaltss.net/gallery/fil...3/pana0288.jpg

Fleece stretched to cover the odd shaped top and bottom.

https://www.cobaltss.net/gallery/fil...3/pana0290.jpg

https://www.cobaltss.net/gallery/fil...3/pana0289.jpg

Fiberglass resin applied to the fleece and then 2 layers of woven fiberglass cloth finish it off.
I trimmed off the excess with my airsaw and a metal blade after it had cured. Then I sanded it up and it was ready for carpet. As for the templates on the wall, nothing for a Cobalt.