I'm about to take on an upgrade of the stereo in the Cayenne.
These things are a pain in the arse because the head unit, amp and stacker all communicate over a MOST fiber optic link. There are adaptors, but they are expensive and have limited functionality.
The factory setup has 9 channels of amplification. I'm going to turf the front center and rear effects (in the D pillars) leaving me with 7.
I reckon packaging 2x 4ch mini amps is going to be much easier than full size A/B amps. Like these:

Has anyone used these? 2ch will be driving the 8" mid bass in the front doors, and I will bridge 2 ch for a 10 or 12" sub in the boot. The clarions have no low pass filters, so I'm wondering about their suitability even if I can use the crossover in the head unit.
At this point I'm leaving the factory drivers which are all 2ohm, so can't run them from the head unit.
Not having cross over controls on the amp is going to make the front tricky too, as it is a 3 way setup driven by 2ch per side.
Happy to look at other options if anyone has any ideas.
Here's what I'm working with.
Click image for larger version. 

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