Aha! Will something like this fit under or behind a seat, perhaps? Time to get the measuring tape out...and if not, camouflaging something so small in the rear shelf can't be that hard?
Not after massive bass or extreme high quality (wind noise and exhaust make such quests pointless) - just bass reinforcement so that I can keep small 2-ways in their original position, running off a small amp in the boot...
http://www.incarexpress.co.uk/view_product.php?partno=TSWX11A
