Can you spare a wheel well Steve? I made a rather nifty fibreglass enclosure for my 12" idmax (11" deep has a huge magnet structure), you could build one for a smaller sub like a 10" and it'd take up f*ckall room.
You can do extractors and tune to get a few more kw, you'll never touch a turbo or a v8, don't let people/companies fool you Pacemaker make some extractors I had em on my old car. Did a little but not much. Good luck
Beware getting a manual you will need significantly more power to keep up with autos unless you're pretty quick on the shifts That's what deterred me from buying a manual in the end