http://www.ebay.co.uk/itm/Nissan-350z-Sound-upgrade-speaker-sub-box-12-10-stealth-side-enclosure-NEW-/151230592165?pt=UK_In_Car_Technology&hash=item23360bb4a5
Just seen this on eBay. Might be of some use to some one.
I think it looks quite cool. Not 'in your face' like under strut ones.
I would probably have it, but I'm not much of an 'ICE' guy.