What should I upgrade my subs to?

[Kickstand Premium Member]

No, it’s a universal bass knob. I’m gonna take some pictures and post it

Try disconnecting the bass Knob and see what happens.
You should be able to control the sub through the HU anyway.
If you can't then just **** it up and deal without it for the purpose of troubleshooting
But set your amp gains according to the instructions the nauc gave after you disconnect it