As a guess, where it is (voltage 20) and the wires would go black on bottom, and red in middle as a guess, judging by the top one saying '10a max' which the alternator puts out more of.
As for replacing alternator, not usually, unless they have lots of power in their system (like 2000wrms~)
I was checking my car the other day, and my power into the amp was 13.3volts. Which I know the car has trouble charging (it's a 35 year old car, it's expected)
And no, the amp doesn't NEED 14.4v to run, but that helps unlock it's full potential as far as I know.

As said earlier, Stock one will be fine for under 1800wrm~
I had an eg8 with stock everything, and that ran 1300wrms~ perfectly. No headlight dimming at all. I loved it. Just make sure you have the right sized power wire to the amps, and adequate earthing, and you'll be fine