[UPDATE] System that came with car I purchased

Firstly, thank you to everyone who commented on my original post telling me about the system that came with the car I bought. I have 0 clue when it comes to this stuff so thank you for all the info. Glad to hear that I got an added bonus with the purchase.

Wanted to update with more pics of the subwoofer and the wiring to the battery. Currently the car still has the OEM head unit and speakers. Hoping to figure out how to get Bluetooth connectivity directly to the head unit. Would also like to maybe upgrade the speakers in the future, would that be easy considering what the car already has?

Also, in case people were wondering. The seller casually brushed over the system in conversation and sold me the sub for 100 bucks. 😁

Pic of the car for funnsies