Hi all, for those on a budget, I thought this might come in handy?
http://forum.retro-rides.org/thread/201177/small-active-sub-budget-bass?page=1&scrollTo=2367057
This thread shows how to strip and rewire one of these...
https://www.ebay.co.uk/itm/2001-FIAT-PUNTO-MK2-BASS-BOX-SUB-WOOFER-SPEAKER-FAST-DISPATCH-MORE-PARTS-LISTED/372050879484?hash=item569ff5e3fc:g:Z4QAAOSw1T5ZmX45
...into another car. If the FIAT box fits after losing to panel, £25 and a bit of wiring, done! Maybe a bit more for a sheet of Mdf if it won't...
I've done similar with a Philips wOOx unit out of a Volvo V40. Cost about £15 all in and I'm happy with the difference it made :)