are you talking of the amplified subs? afaik, it costs around 5k-6k. and afaik, if you are going to really add this to your car, might as well go for the amp-sub way para may expansion ka pa or room for improvement.

what i am recommending, instead of this scenario is to do the "clarity" way. upgrade mo na lang speakers mo to a separates/coax + tweets + aftermarket 6x9's. mas maganda ang tunog considering yung requirement mo.