Thank you Drummernaut.

I think that will work. How did you find out it was 50W @ 4 ohm?

Here is how the Vans radio is wired with Premium Sound without rear controls :

Does any one know the specs for the factory amp from a 2004 GMC Safari for the Rear Door Subs.

GM Audio Amplifier Model 16228175 / AMPLIFIER ASM-LOW FREQ AUDIO

I looked everywhere with no luck.