Thanks again for all the info and advice guys.
I probably should've mentioned that i already have a Kenwood head unit, and I have sourced the bose amp and sub for the tidy sum of £30 all in
this is partly why I thought I'd do that rather than aftermarket stuff.
I also need to fit a pram etc in the boot so thought it might save a bit of space too.
That spare wheel sub looks like an ingenious contraption, but im trying to work on a really tight budget. Plus, isn't OEM the new chrome?