Can u adjust factory sub? Speaker upgrade?

[pete280]

Hi all,

I have an 04 with the factory sub under the drivers seat and rear DVD player.

I'm a little dissapointed in the audio sound, the volume has to be pretty high for the sub to come on then it just vibrates my butt!, works better with movies but not so good with audio.
Is there a way of adjusting the sub level to make it louder or cut in sooner?

Also, what are the stock Rockford Fosgate speakers like? is upgrading them worthwhile? ifso any suggestions? I dont want to change out the head unit.

Last question and i think i allready know the answer, is there an input on the factory Nav screen for a back up camera?

Thanks all

Pete