2008 smart passion coupe

As I understand this car has a 90 watt alternator and I have my subwoofer and amp I want to install. The amp is a Sony XM-D90001GTR mono driving a single Pioneer TS-SW3041D sub woofer in a sealed box. If I turn off the heater air conditioner lights etc. what can I expect from the subwoofer output? Low volume? Can it be ran at a low volume? Will it just kill my battery? I am talking to the dealer via email looking for an alternator upgrade haven't heard back yet.

Found my owners manual on the Sony XM-D90001GTR. It states current drain at rated output: 95 Amps (at 2 ohms).  The  Pioneer TS-SW3041D sub woofer is 4 ohms. Just guessing, would I be using about 48 amps at rated output? The manual states the maximum output at 4 ohms is 950 watts. Supply voltage 14.4, 550 Watts RMS (20Hz - 200Hz at 4 ohms). This amp is a mono class D. It has 3 - 30 amp fuses 90 amp total. With a factory head unit and high level inputs to the amp maybe this will work if I keep the volume down. Maybe? Appreciate any input please.