You have to ask someone who actually owns a 300.

It will work fine with the factory nav head unit. I'm not sure what setup you have from the factory, but I'm assuming it one of the two with a factory amp( BA6 or BA8) . You can pick up the pre-amp signal with a converter and still have steering wheel controls and bluetooth (if you have those options)

Here is some reading material that shows what wires to tap into: http://www.300cforums.com/forums/car...-upgrades.html

If you are going to pick up the signal before, the amp, I would suggest some type of signal processor because you will loose that function as well as the ability to fade front-to-rear because these functions are handled by the amp and the can-bus system.

Hope this helps.