At which point does the OEM alternator become the weak link of the electrical system. Please share if you have experience.

I will be picking up my first crossfire this saturday (2004 SSB 6-speed coupe ltd) and have already been pondering my future audio setup. I will be installing my kenwood x9993 headunit, Boston acoustic SPG555 subwoofer and passive radiator in a 1 cube sealed box and will be powered by my alpine pdx 1.1000 amplifier at 4Ohm. My plans are to have 2 guage wiring ran from under the hood to my Kinetik HC800 battery and then to the Amp itself, just like in my previous vehicle

In my previous vehicle 1994 ford ranger. I was still experiencing some light dimming with this setup and I assume a truck would come with a beefier alternator than the xfire. I have also heard people complain about the weak output of European auto electrical systems. Does that hold true for the Xfire?

In the future I will also be running the Alpine PDX 4.150 amplifier for the highs. If any of you believe that this setup (1600 watts RMS) will overload the electrical capabilities of the car could you explain where I may need to improve or places where you have experienced trouble when running High wattage setups.

As of now I am still fairly new to the car audio segment and have much to learn.
With that said I still expect the OEM alternator to be my first possible problem