Amplifier/Subwoofer installation

1989 Rivi. It has the CRT touch screen-radio system, and I have since installed a 12 disc JVC disc changer. I have an Alpine amp and Rockford Subs, and wondered if anyone knows an easy way to wire this amp in the trunk. I wonder if maybe I can wire it into the power antenna wire thats in the trunk? The main reason I'm askins is, because the changer has no RCA preouts, and I really want to wire this sytem up.