2018 Audi A3 Stock Sub Upgrade, Check My Thinking

I have a 2018 Audi A3 with the Bang & Olufsen upgraded system. This system is actually pretty good, however the subwoofer range is just not what I am used to. I cannot hear stuff in the music that I know is there. Time to upgrade.

My plan is to take the stock subwoofer signal from the B&O amp and route to an Audio Control LC2i in order to add an amp/sub upgrade. When I pulled the back dash apart I found a 4-Pin connector with 4 wires feeding into the stock sub, not 2 as I expected. The 4 wires are...

white - grey stripe
brown - blue stripe
brown - white stripe
blue - grey stripe

I sprung for a 24 hour erWin subscription and downloaded all of the manufacturer documentation on my car. In the communications documentation I found that the Bang & Olufsen 9VS system amp/control module has a 38-pin connector where pins 19-22 go to the subwoofer with their polarities listed. I then found a bit more in the wiring diagram file. Eventually found a page that showed pins 19-22 on the 38-pin connector terminated at a 4-pin connector at the subwoofer. Combining the two sources I pieced together that...

Pin #19 @amp = sub (-) = white/grey = pin#1 @sub
Pin #20 @amp = sub (+) = blue/grey = pin#2 @sub
Pin #22 @amp = sub (-) = brown/blue = pin#3 @sub
Pin #21 @amp = sub (+) = brown/white= pin#4 @sub

My assumption is that...

The sub has a left and right audio channel wired to it
The blue/grey and white/grey wires are a +/- audio channel
The brown/white and brown/blue wires are a second +/- audio channel

To hook up the LC2i line converter all I need to do is wire one pair to the left channel input and the other pair to the right channel input. The LC2i will do the rest.

Think I'm on the right track? Thoughts?

You can "pop" the sub with a battery to verify polarity.

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My ex once told me I have a perfect face for radio.