sub with out a box..are there woofers are made for it???

[KenC]

another option is two six by nines in the back, and run them off of an amp.

99% of the 6x9s out there are crap. I don't understand why people mod the rear deck so much to fit them in. You can run a good 6.5" on a low pass (~175Hz) and it will reproduce much better quality sound.

Or you could add an 8" or two to the rear deck. Keep in mind that you'd have to build some sort of custom shim to avoid the magnet hitting the trunk mechanism under the rear parcel shelf.

Your best option would probably be a 10" sub in a small sealed box. A ported one will sound better, but it will have to be a little bit larger.

I'm still not sure why you're worried so much about adding a little bit of extra weight.