Im going to be doing something similar on upgrading system soon. I will be eliminating the factory amp out of the loop. I tapping into the pre amp signals also. I originally just wanted to just unplug that big square connector at the factory amp and find a connector to just plug in and make my own harness to my amp-etc. Without having to splice into the harness, after a lot exhaustion cannot find a plug at all- the only way that you can get it from Honda is with an amp. I don't want to cut my pigtail coming of my factory amp, I case I ever want to go back to stock. If you or even others on here are just going to throw away or sell very cheap, I could use a donor amp for the pigtail with connector. I think I will be going the posi taps at the wiring from just out of the preamp (just for the front and rear channels) and just unplug the factory amp and leave it in place.