1. Yea they have RCA splitters for that. 2. I wouldn't use the rear 6x9s if you're using a sub. 3. It doesn't matter if you run a 5k rms amp on a 500 rms sub lol you will be ok. 4. I don't know if I missed something but I would just run a 2 channel (unless you want to go active then 4 channel) for the front speakers and a mono for the sub. Not sure why you would need all those amps. 5. Fuck the capacitors. It's useless. Someone can explain better than me why they are. 6. Speaker size is good. 7. Same ground is fine. Just make sure it's good and not some flimsy sheet metal. 8/9. Not really sure what else would be missing. Gave advice above! Hope that helps