how big of a alternator

Ya iam putting a 2000w RMS amp in my car and i would like to know how big of a alternator i can put in my car and iam putting 1g wire from alt to bat please help Thanks Stump

i know for sure you can use a 160 amp alt. not sure if you can use a bigger one

The alternator you have is plenty big enough for the job.
You need to install a 2 farad capacitor to make sure that the voltage stays as a steady level. Usually 1 farad per 1k wattage is good enough. You would be ahead to connect the amp to the battery not the alternator anyway. This way you have constant voltage even when the car isn't running.