I don't have a spare tyre or tools in my rear wheel bay so I was thinking of filling it with a nice big sub if it's was possible? I just wanted to know if its worth doing? will it sound decent? how much it should cost and how to do it? I fancyed getting a 15" if it will fit in the spare tyre space and a pair of 10 or 12 inch subs either side in the boot. I've got a 214 si btw.