Answer
I agree with a2wickedbad, if you want to install an amplifier with your head unit at least you should get one with 2 set of pre amp outputs (front left & right, rear left & right ) to connect the to the amp pre amp inputs. some expensives unit have from 2- 4 v of pre amp voltage. make sure the amplifier supports the maximum output voltage of the unit, some of the amps are only capable of getting 2 v pre amp.
look for the features it has like mp3, wma, ipod ready, xirius ready, eq.,, to the power in rms per channel, aux inputs.
