Ok, I got the 7800 about 3 days ago and went ahead and installed it myself. Everything was pretty straight-forward as far as cables. There is only one question I have right now. Below is a pic of some of the cables on the harnesses that I used. I only drew some of the cables to make things easier. Basically, the HU will not dim when I turn on my headlights. I connected the orange/white from the Pioneer Harness to the orange/white labeled "dimmer" on the Metra Harness. This did not make the HU dim. Then I used the orange marked "illumination" on the Metra to the Dimmer" off the Pioneer HU and still no dimming. I also made sure the dimming feature in the HU itself was turned on also. Not really a problem, I can deal with it I was just wondering if anyone else with this HU can dim their HU when they turn on their headlights. Thanks.
Everything else is working just fine, this is the only thing. Also got my KnuKonceptz 4ga Amp Installation kit today and I went ahead and ran my wires so I'll be ready to just drop my amp in once it gets here. Hells yeah.