GM Class 2 CD Changer

When did GM start using these? I'm trying to add a changer to my 2003 Impala, and have been told it will only accept a class 2 changer. The plug on the end of the changer cable is the same as the changers in my '95 & '96 Pontiacs, but the '96 changer did not work when I plugged it in. I can't swing $300+ for one of the aftermarket changers. Does anyone know what GM cars had a class 2 changer installed (I need the 12 disc Pioneer type so I can swap magazines between changers).

Thanks in advance.