Just one more thing to add.
I'm using a Y Link subwoofer cable which I had lying around instead of buying a single RCA to RCA.
The Y Link I have is a PPX to 2 RCA. It's this cable here:
It's not any harm to use that connection between the amp and the sub is it? It won't affect performance in any way?
I have the PPX on the amp side and both RCA's fed into the left and right inputs on the sub.
Both inputs on the sub are black by the way, and not red and white, or red and black like you see on some others.