Hi all! Building a 5.1 system, turning to the experts for my Subwoofer

I've always enjoyed nice headphones and sound, but never considered myself an audiophile. This has changed recently, as I got a hand-me-down Yamaha PF-800 turntable. I spent a ton of time restoring it, but realized I needed to have the system to support a piece of equipment like this. So, with fantasy football done, holidays and vacations over, and having recently finished a long video game, the conditions were perfect for me to fall down this rabbit hole.

My current setup is a Yamaha RXV4A receiver from accessories4less, two hand-me-down Yamaha NS-10M's from my mom's attic, a PSB Image 9C from facebook marketplace, and a PSB Subsonic 8 also from facebook! Might hawk the LR from a cheap 2.1 I built on my desk for my 5.1 surrounds.

Really need help with the PSB Subsonic 8 though! It doesn't power on, but I understand why (I think!) I do not, however, know how to navigate the circuitry to fix it up! Looking forward to talking and learning from you all.