I've seen and heard a swiftech close loop system, those are pretty quiet. I might go that route, if the Kraken is that loud. Anything is probably quieter than 80%~100% fan speed of a reference cooler...lol
I wouldn't consider the Kraken loud at all for a mining rig.
It's reasonably quiet for a gaming rig, rarely needing to be kicked up to 100%, if ever.