adding 4 channel amp to 2010 camaro

I'm trying to add a 4-channel amp to a newer model Camaro and I have some questions. The basics: This is not a factory amplified system so non-BA (Boston Acoustics) 4-channel will be added to the factory head unit However, the door chime, OnStar, bluetooth, etc. come through the speakers and the customer would like to retain these. So my question is, how can this be done. It's easy enough to grab the rear speaker inputs from the rear deck. However, my concern is the front speakers. I would have to use a 4-channel line out and i've looked up the Pac Audio AA-GM44, which is a T-harness. If I use that harness, I would only have RCA out. How would I go about grabbing the speaker level inputs to run to the amp? That's basically my question, where/how would I go about grabbing the speaker level inputs?

If you're using the Pac Audio AA-GM44, then you use those RCA outs to your new amplifier and won't need to use speaker level inputs.  Then speaker wire would be run from the amp to your new speakers.Rob