So I have a factory amplified system. I've decided I want to upgrade the whole thing. I don't want to retain anything from the factory system. Would I be correct in assuming that when I get a new head unit. And my own amps for the sub, replacement speakers in factory locations, and some additional mids/highs I can just continue the install like you would in a car without all these extra electronics. I keep looking and everyone keeps trying to sell me these adapters for the factory amp among other stuff. Not only does that over complicate the install. It cuts into the budget significantly.
I don't know your specific vehicle, and don't expect any general audio information does either, unless they specifically know your vehicle, or you went to get information from somewhere that does.
IN GENERAL ON OTHER VEHICLES, there are modules(/adapters) for several different things. They can retain factory warning chimes, if the noise comes out of your speakers. They can be needed to retain steering wheel controls, because mostly what those do is convert an analog signal from your vehicle's controls into a digital signal that your new head unit can understand. They can be used for media screens, navigation, or for converting a signal from your factory amp to your new head unit.
As for needing one for the amp, then no you won't. As for needing one for some other feature on your vehicle, you might.
Two of the companies that make these are Pac-audio and axxess.
catalog.pac-audio.com
I see they have a few options; one being the steering wheel controls, and another being an amp. You should read over these. There's also no reason you can't add the steering wheel controls module, later on down the road, especially if you don't use it. You might lose some warning sounds such as lights, or doors, (if you enjoy those), not sure on your vehicle.