Case Fan Configuration with CPU AIO

I have a PC with 3 PWM case fans plus a Kraken x62 AIO. Currently the fans get louder than you would expect with an AIO. I have adjusted the fan curve but it isn't helping.

I contemplated the fact that maybe going off CPU temp shouldn't matter and so I should adjust the fan curve off ambient. My motherboard came with a couple extra temperature thermistors and I could use one and adjust fan speed based on ambient in the case.

But if CPU usage goes up, the AIO should regulate itself on its own. So the case fans I would assume would not be part of that equation for the most part I would think.

What do you think?