Audio Systems: hooking up an amp to a 2007 Chevy Impala, factory radio, chevy impala

Question
I just got a new 2007 Impala, but I wanted to hook up my amp & sub-woofers to it. I have on-star & XM built into the factory radio so I dont want to change the head unit. What I need to know is if there are audio output jacks on the back of my radio & if not, can I hook up a low level adapter to the wires running to the speakers in the trunk without messing anything up?

Answer
no there is no rca out jacks  and you can not use any regular low level adaptor,  it don't work and you get beeps and noise on the audio line  
be very carefull when working with this radio is very easy to get damage very expensive unit and not easy to replace it is not just a radio  
your radio is part of the electronic system of the vehicle and air bags and other warnings

i have a link for the part that you need to add the amplifier
good luck

http://www.oemautosound.com/pc-217-135-pac-c2a-gm24.aspx