I am putting in a single "12 sub in my trunk but I'm worried that I won't hear it as well as I could. The seats don't flip down and the fuel tank is against the back seat. Should I be concerned about sound quality due to the fact that the trunk is separated by the fixed seats and the always full gas tank?

 

I have a 10" sub mounted in the far rear driver side corner - no problem at all hearing it! In fact it's amazing how loud it pushes...