[Ashallib]

Hello all this is my first post on here so bare with me... About a year ago I decided to take on the task of wiring my own subwoofer and amp I got off of marketplace. I foolishly did not do enough research and sped through the wiring without much regard for what I was actually doing. I ended up pretty much cutting the whole wiring harness for the factory amplifier behind the back seats that I thought only powered the door speakers. Now my dash speakers are no longer being amplified because I removed the factory amp. Does anyone know if there is anything I can do still or is it too late?

Thanks in advance
Info:
Car: 2013 mt premium BRZ
Sub: Alpine S-W S-Series Dual 4-Ohm
Amp: Boss R1100M