Upgrade the head unit, polaroid audio speakers, and adjust the equalizer- but without a heavyweight subwoofer, you will always feel like you have left out a piece of the puzzle with your car sound audio system. It is not only about blunt thumps, but depth, clarity, and balances that bass is all about. The right subwoofer translates the music that you are hearing into one that you are feeling. But what is the correct one to pick?
Let us consider it one step at a time.