We're getting a tad carried away here. Running a single Alpine amp is not going to require 2AWG cable.
As for the cable itself, much like everything else, you'll pay for quality. Realistically for wiring an amp up, including the speakers etc will set you back between $130-$200 for brands like Stinger and Phoenix Gold and between $250-$330 for brands like Streetwires.
JR, you asked where you can get 2AWG from? I can get it for you from any of the above mentioned brands. I use 1/0AWG in my own S15.