Need some help

I'm planning on putting a 2000RMS Watt system in my car. I did the math on how many amps it would be pulling and it's around 150A. I know i'll need more power in my car and was thinking about upgrading my alternator to a 160A one. Does anyone know about how much this would cost, and would there be any other things I should be thinking about? (no worries on the wiring and the Big 3).

My car is a 97 Chev Caprice, 5.7L 8-cyc.

(P.S. I also am planning to put an extra battery near the amp to supply extra juice when needed, in the trunk.)

that amp draw is a max figure, but a 150 Amp alternator should be fine. I really have no idea what a new alt would cost these days.