Volvo car audio info needed: 2 factory amps for 1 system

[CIK7]

I want to incorporate both of my 4x100W c70 amplifiers in my trailer build. And this is just for the first four channels and not the fifth for the subwoofer. That's a separate amp.

First, I would like to know what that amplifier connector is called because I want to find a dual to single dongle.
Now to the meat of the post. I want to make sure it's safe to combine both of these amplifiers to get one front left, front right, rear left, rear right. I'm planning about 160-180W per channel. See attached pictures.

P. S. - I just NOW realized it could be difficult to bridge 2 amp-to-radio harnesses with an additional sub amplifier needed to wire in. Advice?