This ^^^U need to bust out a tape measure and see what all as far as room you are willing to give up and then see what your sub options are. There are mnay subs that dont have a deep mounting depth or require a massive box but are not "shallow" subs which I would never run.
I have a civic and I can fit over 3.5 cubes. My biggest issue was height of the box.hmmm yea its just sucky cause I have a honda fit so trunk space is hard to come by with big subs but I want a nice sound still to