Wiring Pioneer Deck in 2011 JBL

So my buddy gave me a hand-me-down Pioneer AVH-X4700BS DDIN head unit that im thinking about throwing in my truck. Unfortunately, it didn't come with any of the stock wiring, so i need to buy the wiring harness, handsfree mic, and USB extension.

That bullshit aside, i've been weighing out my options for installation. I am satisfied with the door speakers in the JBL system, but the stock subwoofer has got to go. I'm eventually gonna pull the JBL sub and plastics and put in a custom box with two 10" subs and an additional amp. My questions are:

1) What is the cheapest way to wire this pioneer deck. i am okay with not having steering wheel controls. will https://www.amazon.com/AXXESS-TYTO-...e=UTF8&qid=1519108618&sr=8-2&keywords=tyto-01 do the trick? Or do i have to use the $100+ dollar metra adapter?

2) When one removes the stock subwoofer, but wants to retain the JBL amp for the door speakrs, what is the best way to go about installing the new amp and subs? To run from the head units RCA outputs? or to tap into the JBL amps signals with a LOC?

Your thoughts and suggestions are appreciated.
Cheers