You can either cut the wires before the amp, or just tap onto them without cutting them. Then run that wire directly into your new speaker. Since it is before the monsoon amp it will be running directly off head unit power and sound way better. Depending on what head unit you have it may even have a built in crossover for the rear channel. If you ever plan to sell the car or anything then my advice would be to just "tap" onto the rear speaker wires before the amp, and leave the wire that comes out of the factory amp alone with the speaker plug on the end still. This will make it easier to install the factory speakers again if you ever want to.
