I just bought a line output converter, PAC SOEM-4, but I need some help with wiring it.

I want to keep the factory radio but run all 4 speakers off an amp. I understand that I have to splice the input of the LOC into the speaker wires and connect the output RCAs to the amp.

This LOC has a remote amplifier turn on wire that gets triggered by a signal on the Purple wire (right rear +).

So here is my question.

Since I want my speakers to run off the amp don't I need to cut the speakers from the radio and connect them directly to the amp?

If I do need to cut the wires from the radio, how do I wire the LOC's input to the factory radio?

Sorry if this is a little confusing but thanks for any help.