this is the perfect time to try my experiment!
If ported gives you a louder sound, and sealed is harder hitting, why not get both?
Just have 2 separate, single sub boxes. Have one ported, and have one sealed so maybe you can get the best of both worlds with the loudness and hard hitting bass...
well if the car has a factory subwoofer it is most likely amplified with an OEM amplifier which may need to be disconnected so you fry the head unit.
but my car has 6 speakers and when i hooked up my head unit all of them still worked and i did nothing different to mine than any other 4 speaker...