My audio setup

[B-R-Z]

It was my assumption that the factory radio sent a low-level signal to the factory amp, this is actually a high-level output so I incorporated a MTX Re-Q (LOC) to fix the signal.

If anyone has any questions\comments\recommendations please share.

Equipment:
Stock radio (BRZ Limited nav unit)
Sundown Audio SA-12 in a sealed box - Link
PPI A600.2 Art Series Amp (It's a dinosaur but it's awesome) - Link
MTX Re-Q - Link
Sound Storm Laboratories SX310 3-way Electronic Crossover - Link
Metra 70-1761 - These harnesses will be used together to avoid doing any cutting to get signal from the factory amp.
Metra 71-1761 - ...

Plug wiring: I pulled all of the pins out of the Metra 70-1761/71-1761 and placed them in relavant\understandable places based on the writing on the wires, some of the wires were not needed at all. Front speakers were placed in front speaker locations and since there is no wording for amp high-level output signal, I used the rear speaker wires for this. For the 2nd plug included with 70-1761/71-1761 (power), I pulled all of the wires out and used the red\black from the larger plugs, some wires are not needed in this plug as well.

I am still on the fence with using the factory door speakers. The bass with these speakers rattle the window up\down switch. I wish there was a simple way to prevent bass from hitting these speakers without replacing the amp.

Harness shot:
The white\yellowish plugs are the Metra harnesses that basically intercept and forward the signal going into the factory amp. They function basically in the middle between the plug coming from the headunit and the amplifier itself. This allows for plug-n-play capability without cutting a single wire.

The black plug with the pins coming out goes into the MTX Re-Q device.

The clear and red wire off to the right side are remote (red) and power (clear) for the Re-Q and crossover.