That is why I went with the 10's plus I got 2 for $102 from circuit city.com
You would have to loose the spare or raise the floor about an inch. You could do that and either have to raise the storage bins in the rear or take them out/cover them.

 

If you have a factory Hu Where are you tapping in for the Sub and what are you using? Where are you getting the 12v trigger (or turn on) from?

 

I do have the factory headunit with the 7 speaker system. I am using the remote turn on for the factory amp as well as the sub outs form the factory amp. I amp running the output to a line level converter then to my amp.

 

Same here.

 

is the amp located in the rear by the sub?

 

yes on the sub box lower left corner

 

This is what I have so far:
http://www.plugnpl4y.net/images/HHR/Picture_150.jpg

I plan on making an amp rack but i was in a hurry and i'd need longer wires.

 

Why not mount it under the rear shelf?

 

well originally i did, and i guess i could put it back. but i needed the amp accessible while the sub was playing, to tune it.

 

If you noticed in my pic, the sub is still there. I just lowered my back seats and pushed the sub back.

Easy access. I had to do this again today because I was taking out the box temporarily and needed to tune my 8" sub. Worked like a charm!