La JOlla audio in La Jolla, CA has suggested two wonderful applications for a z3...both require expensive installation. The first suggestion included cutting several small holes in the metal(honeycomb like) between the trunk and where the top folds down to allow the subwoofer to moveair in the cabin. So many people i know have tried to just put a sub in the trunk and they get a wonderful rattling license plate and that is about it. So a 10in mounted to fire into the cabin would be a good option....expensive intall factor: 8.....The next option they suggested to me is what i have decided to do. They say that between the firewall and the passanger floorboard, exists enough space to hide an 8 or 10 in sub. They would remove the carpet, cut through the floor, build an enclosure, place some mesh over the sub, and replace the carpet. You have a sub firing towards you, not behind you, in the cabing, and totally hidden. Sounds good to me. However the sub install is going to be about $1500.00 or so, so it is definitly for the enthusiast....cost factor: 10. Hope these two options sound good. A bazooka on the floor is a great option if you dont mind in being visible. I believe that it is not worth fixing the hk system. Unfortunatly a quality sound from the z3 is expensive, but attainable. email me if i did not explain things well enough. sorry bout my typing i am to lazy to go back tom