I have a Kicker L712 solobaric (square sub) that I am going to attempt to somehow get in the Lightning. I had this in my Denali, so I am going to try my best to get it in the Lightning somehow. I will keep you all updated as to how it turns out.

 

I saw a 10" in a "truck box" that wasn't very thick. I would imagine a 12 would fit behind the seat ok. I like the sound of the 10's, never heard a 12.