You should have a Birth sheet/Performance sheet that came with that Alternator when you got it. It should tell you what voltage that regulator performs at during certain RPMs when tested before it was sent out.
Id look at a 800-1000 CA, 750-900 CCA, and at least 120RES Starting AGM battery , and put that XS as a reserve as a secondary and main supply at the amplifiers. you shouldnt get any dimming out of your lights at that wattage.. Should be good up to 3-4k RMS on all your amplifiers running
@Full Tilt maybe low @ 12.6 @idle. If lights still Flicker and voltage is good.. Those HID or LED lights may need a Relay to stop those from flickering.. Like a 40 amp relay( prob like $6 bucks at Orileys).