Upgrading audio

If upgrading audio system is the backseat and the lift gate speakers separate? Meaning do I need a 6 channel amp? Or 4 channel amp? Because I know the front doors and dash tweeters are considered fronts. 2019

 

As far as I know the fronts are the front doors and dash and the rears are 2nd row doors and lift gate. I'm looking at getting a small class D amp and fab up a harness for the speaker inputs
for a temporary solution. 5 channel if you want a sub.

 

So the liftgate and the rear doors are run in parallel? So all I would need is a 4 channel amp? And I'm going to go with a jl audio 10w7ae3 and a amp bridged for 500watts jl audio. Just wasn't sure if I wanted to spend the extra money for the liftgate speakers. But if they are wired parallel then will do so.