Thanks guys,

What I am (or was) trying to do is exactly that - kinda. I have options, but was just suprised at the outcome of my little test.

I wouldn't mind replacing the infinity amp if I have to, so the correct thing might be to run the factory head unit into a line-level converter, then into my active x-over, then into two new amps (one for speakers, one for sub).

What started all this, was the thought that I might just be able to run the sub amp by "piggybacking" and stealing signal from the factory system - essentially leaving the factory system alone. (Why, you ask? It sounds pretty good actually, and I like having the steering wheel controls. I know PAC makes the adaptor to make them do IR too, but I have only 5 buttons, and cant figure how Id make that to the empeg in any useful way)

So, If I turn up the volume to say 50-70%, and play a nice sine wave, and measure the output of the stock head unit, I should get some voltage, correct? (I'd be measuring AC?)

"line level" is what, 1-4volts or so? Should I make this measurement with the head unit connected to the inf system or my aftermarket amp?

(I trust that they are "in between" but I'd like to measure it anyway, just to see)

Thanks-
Jeff