Here is my 2 cents on this topic. I removed my rear seats and my rear deck. I used a razor blade to carefully remove the cardboard/jute backing from the first aid kit door (leaving only the acoustically transparent carpet). When all is said and done, you can not even tell there have been any mods to the first aid kit area.

I am waiting for a Infinity Basslink sub to arrive (small 10" sub enclosure with a passive radiator, built in 200 watt amp and accepts high level signal inputs), this unit will be mounted under the rear deck and fire up through the first aid kit opening. Simple install since this particular enclosure has mounting brackets for horizontal or vertical mounting. No compromise on trunk space and you can tap into the factory rear speaker wires for signal inputs. You do need to run at least a 8 guage power wire from your battery though.

I picked the Basslink up from Ebay for $234 shipped. It has not arrived yet so I can not comment on the sound. I have extensive pictures of my speaker/sub mods so far but have not put a web page together as of yet.