Has anyone still experienced dash lights dimming even after electrical upgrades?

Already installed:
High output alternator
Car audio battery
Cap at sub amp
1/0 amp feeder cabling and alternator cable upsized
Ground upgrades both qty and 4ga
Sub amp is JL 750HD which is efficient

Starting to wonder if its just filaments vibrating. Sub is JL W7 and it hits hard enough to bounce windshield wipers so who knows.

Guess I need to borrow dc amp meter and see what kinda loads I have at full bass.