sorry i'm a newbie regarding into car audio.

i had my 2011 toyota innova G installed with a firland audio EV 602 separates, NV-10-A-480 4ch amplifier and a 12' Firland Audio 1280 series subwoofer last wednesday. i am currently using the stock HU of my car which has a maximum volume of 63. my subwoofer is currently in the break in period.

my questions are:

1.) the maximum volume of my HU is 63, so what must be the volume of the HU while i'm listening to the songs and the subwoofer is in the break in period?

2.) someone told me about the voltmeter, do i really need this one in the kind of set up i have? the maximum volume of the HU is 63, so to be safe and to avoid burning while i still don't have that voltmeter, what is the safest volume while i'm listening to the music? is the 70% of the maximum volume of the HU will do?

you know, i love to listen to the song's bass, so sometimes i am being tempt to increase the volume for more. :D

sorry for the ignorant questions, hehe. thanks for those who will answer these. :D