9 wire vs running new wire

So I don’t even have it yet but I’m going to be buying my father in laws ‘13 Sentra it has factory nav so I’m going to be keeping the stock deck in place (first time ever not having an aftermarket deck) and using a lc2i. For subs I’m gonna run a JL Audio w6 12ae in jl factory box ran off a Jbl 751ez amp.

I’ll eventually upgrade the speakers and run a 4 channel but I’ve always ran new wire because I’ve had older vehicles that are easy to take apart and don’t have to worry about fudging them up in the process. I’ve never used 9 wire and even though I’m not gonna be running a ton of power the highest awg I can find is 18 same as most factory speaker wire.

Thoughts?

Who else uses 9 wire?