Have a look at the Rockford Fosgate section on here,
www.audioethos.co.uk , the BP1000 bass tube he has is as light as they come and kicks really low and loud,I use one in my MK3 and it's better than the twin 10 inch Vibe Black Air subs I had previous,and it's seriously under rated on the rMS power side,my amp puts out 400WRMS and it handles it all with no distortion.