2002 nissan xterra

I have a 2002 nissan xterra with a rockford fosgate system that is factory it includes an indash changer and a subwoofer. My question is , can I replace the headunit with my aftermarket alpine without replacing any of the speakers or bypassing the amps and sub. My reasoning for this is that the Alpine is mp3 compatible and so is the ai net changer. I also like the alpine much better than the rockford that is in there. If someone has worked on one of these please post any info that may be helpful.  

                                                                                                                           Thank You

I believe that the stock rockford amplifier just uses an RCA type input and thus all you'll need to do is hook up your alpine's RCA outputs to the stock amp, and figure out which wire is the remote turn on wire for the amp, and you should be good to go.  I'm not 100% sure about this but from what I've read and heard, it just has these simple RCAs.  The stock amplifier is supposed to be located just underneath the head unit, so I'm betting once you remove panels and stuff and can get a good look at it you'll be able to tell right away whether or not it does indeed have RCA inputs.  If it does not, you're looking at a more complicated integration setup, but it could probably still be done.

I would not recommend trying to bypass the factory amplifier as the speakers in the vehicle are not the standard 4-ohm automotive speaker, and this could pose problems for your Alpine head unit if you were trying to directly power the speakers using it.  Also, you would lose your subwoofer if you bypassed the stock amp.