I just installed on a 2000 GT - to get round replacing the Mach system I had a new Radio\CD installed (with Aux In), hooked the empeg into the Aux in, then installed the coverter between the Radio Out and the factory amps.

Upside - it works and is easy to go back to factory if I sell the car

Downside - was just as expensive to install as buy the empeg (but worth it)

HTH