When I started on Harley it was sitting in a dirty warehouse and the cab speaker was disintegrated. I replaced that with a random subwoofer I had jn my shop, but the game amp wouldn't drive it well
I added a Pyle speaker to line converter, and Diymore TPA3116DA 100W Mono Channel Digital Power Audio Amplifier Board. Also, an L-pad in the backbox to balance the levels between backbox and cab speakers. I'm powering the amp on an independent 1.2A supply (again, from the parts junk pile Altogether less than $60.
It works great, just need to clean up and mount everything.