Ahh OK fair enough, so its an aftermarket head-unit then. What you will need is an RCA cable (2 male - 2 male 5m length) and a pair of RCA splitters (1 female - 2 males). See below for links. You connect the RCA cable to the preouts on the back of the head-unit and then "split" each RCA plug into two plugs using the splitters, then connect the 4x plugs to the 4x RCA inputs on the amp.
5mt OFC Pro Series RCA Leads Car Audio Lead - Jaycar Electronics
2 x RCA Plugs to 1 x RCA Socket - OFC Y Cable - 300mm - Jaycar Electronics
Oh yeah, and you'll need to connect each driver (speaker) be it a normal speaker or subwoofer to each channel of the amp. So the rear speakers on the parcel shelf go to the "front" L+R outputs on the amplifier, then one subwoofer connects to the L "rear" output and the other subwoofer connects to the R "rear" output of the amplifier...i can draw up a quick wiring diagram if you like.
Also, have you got the "REM" input on the amp connected to a wire that turns on with the ignition, or connected to the blue wire coming out of the head-unit?
This tells the amp to turn on and off with the stereo, and dosent stay on when the stereo/car is off.....this will result in a flat battery fairly soon.
