Do car manufacturer have "Pre-Out" in their HU?

[Gregavi]

More specifically, recent auto makers from, say, 2015 to 2019?

When upgrading a vehicle in recent years, if there are no "Pre-Out" in the HU, are there any options other than scrapping the entire HU and starting over? It would be a shame if the stock system has a NAV and other modern technology features integrated into the HU that would have to be scrapped in order to improve the amp part of the system. I assume most of you here would not recommend running the system through a "Speaker Level to Line Level Converter". How else can the amp section be improved if there are no "Pre-Out" in the HU?
Thanks in advance.

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[BCotrell]

What car is it, lot of cars have plug and play connectors from companies like pac audio. If you are post factory amp signal, there’s products that do signal summing, and for super basic factory radios you can connect aftermarket amps that have high level inputs

 

[Popwarhomie 5,000+ posts]

Plenty of ways. With my ST I had to keep the factory touch screen nav system so I bought a Rockford DSR1.