I was considering a bluetooth camera, but they seem to cost a lot more, and then there are all the issues with it being wireless vs wired. I'll keep doing research on that.

As far as the amp... do they come smaller than a 10" x 9" x 1"? I'm worried about finding a spot to hide that behind the dash... Anyways, would something like http://www.amazon.com/Desert--S900-4-4-Channel-Multichannel-Amplifier/dp/B00VPYTOS4/ref=sr_1_2?s=car&ie=UTF8&qid=1445394198&sr=1-2&keywords=4+channel+amp work?

And yeah, I've found a ton of roms for this purpose and am very familiar with flashing androids. I just need to find the right combination for my purposes!

And finally, I think I have it all diagrammed out... so let me know if anything sounds weird here :) Radio Wiring Harness specific to my vehicle will have the following connections : ACC ON, Ground, 12V, and individual speaker connections. I'll get one of those car chargers for the nexus, and wire the ACC ON and Ground to it, with the usb end going to an OTG cable connected to the nexus and a usb hub. The usb hub will connect a DAC which is connected to the AMP, which is powered by the 12V (or should I use the ACC ON again?)/ground, and the speaker wires. The USB hub will also be wired to the glove compartment to attach usb drives for music/video/etc. If I go with a wired back-up camera, ill need a converter to bring the AV video cable to usb, and that gets powered by the reverse light power cable. If I go bluetooth, I can go without the AV cable since itll just pair to the nexus.

Really appreciate the input!