PA series rads require high RPM fans to perform at peak peak. I'd look at nothing less than a solid 90cfm, preferably 100-120 to get the most out of it.
I know mate but my ears want a break! The fans are quiet with the controller during the day and evening, but at night when you want to just chill and watcha film or something and it's quiet, they seem too loud!
I'm removing my gfx card from the loop now so thats less heat to dissipate, so hopefully 74cfm should be sweet