OK... one more detail.
I had it hooked up and it worked fine... however, when I turned off my iphone, the amp turned off and wouldn't turn back on on its own. Apparently the signal from the iphone's headphone jack isn't strong enough to trigger the amp's "signal sensor" turn on method.
Solution? Run another 12v wire from a 12v source, that is part of the ACC (key on) circuit, to trigger the amp. I'll be doing that this weekend, but that will solve the problem.
So... two total mods to car: Run 12v from battery positive to amp. Run 12v line from an ACC source to the amp's "remote" input.
Pretty easy.