Install Alpine KTP-445u power pak amp

hey i have a 2015 Toyota Corolla s. I am running Rockford fogate component speakers and 2 Rockford fosgate 6x9 in the rear deck. I also got 2 10" type r w/ a Rockford fosgate mono amp. I bought a 4 channel alpine ktp-445u power pack to power my front and rear speakers. have any of you installed this amp or something similar into your factory head unit ? I bought mine the other day and I am a bit lost.

Here's a picture of the back of the head unit for reference

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I know that there are 2 sides of the amp.

1. This wire harness on the amp connects to the speakers (green/greenblack = rear left speaker, etc...)

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So my question is what harness behind the head unit do I cut and re wire with the harness on the amp?

Also since The speaker wire is running to the amp now, whatever harness that was on the stock head unit would be vacant right? Cause it is no longer running to it?

2. This wire harness on the amp connects to the head unit and it is used for the input.

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Since I am still running a stock radio, I would need to cut the RCA plugs on the amp and wire them straight. My question is what harness Behjnd the head unit do I wire with the cut RCA wires on my amp?

3. Where do I connect the Yellow ( POWER) cable? I don't want to run it to the battery but to the head unit.

4. I am also also running and high low converter for my mono amp powering my subs. Do I keep this or remove it ?

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Thanks in advance for the help!
I'm no longer using the high low converters it... IMG_0872.JPG Before you cut the factory wiring harness, get a set of adapter harnesses. IMG_1214.JPG These are inexpensive. I think I paid about 5 or 6 bucks each, but can't remember where I got them from. I'll let you know if I remember. IMG_1213.JPG One will plug into your factory head unit and the other will plug into the factory wiring harness. Make all your splices to these adapters.
Then get you a set of Kicker KISL 2-Channel K-Series Speaker Cable to RCA Adapter or equivalent. You might need two sets. They're $10 on Amazon.
I was using the high low converters at first but they sucked. So I went with straight wiring. Once you've added the RCA's, you can use an RCA splitter to send the signal to your sub amp.

Your stock head unit only puts out about 18 watts per channel, so there shouldn't be enough voltage to damage your amps. Most amps have a 5 volt limit on the input side.
I'm running this way and have had no problems. I have a Kenwood 4 channel amp mounted behind the glove box. A Kicker mono amp in the trunk. Kenwood 6-1/2 components front and rear. Kicker 12" loaded enclosure in the trunk. Sounds like a concert!
Also, the amp turn on wire should be connected to the head unit via the blue and white wire of the adapter harness. And the adapters will plug into that double connector on the right of head unit. (in the back, based on your picture) Amp power should come from your battery and make sure you have a solid ground connection! Most important!
Should be bare metal, I had to scratch off some paint with a wire brush.