Post a video of it playing at high volume you usually use so we can see how the sub is moving, and listen for any possible clipping as well.

I'm willing to bet everything is ok with the car besides not having enough power in the electrical to support the dimming, a 2nd battery like a kenetik HC650 would most likely fix it im willing to bet.

The new punch amps aren't as underrated as the old ones. Back in the day of the old gray waffle iron heat sinks they were underrated by nearly 100%. But not anymore. Rockfords have always also been a bit current hungry. Yep, I just looked it up, and as per Rockford's website, that amp is only 65% efficient because it's a class A/B. So you're pulling about 500 watts from the electrical system. Are you clipping the hell out of it too?

Yep on both accounts.

So how much more ineffecient would a Class AB be then a D?

I have the same problem with a Kicker 300.1 but i also only have a 65 amp alt.

Sorry not trying to threadjack.

A/Bs are generally about 65% and Ds are around 85%.