back seat sub box!!
i don't have any pix right now cause they got deleted but i'll try and post some up tomorrow
You will get the most output, not to mention sound quality with them mounted in the far rear.
I doubt there is enough air space for 2 15's much less 3 in the far back. How much space does each 15 need? If you don't have the room, then probably 3 15's in the rear seat area will sound about the same as 2 15's in the far rear or close enough. You'll be moving a lot of air, that's for sure.
You can hear me coming down the street with one 12" and 300w.

That's with quality equipment, though.
First, fiberglass is your friend.

Next, I have two 15"s myself. See my sig.
If you were skilled and willing to do a couple things... you could get about 6.5-7 cubes back there. 


