The Kraken X42 is a great closed loop liquid cooler. That said, the 7700K tends to get a little bit hot. It's factory overclocked by quite a bit, and has a thermal paste instead of solder between the die and the IHS, which is not as effective as solder. Anyhow, 70C is perfectly fine to a CPU. I'd say up to 85 is considered safe. If you want to reach lower temperatures, you have three options. Increasing the fan speed (or adding an another fan to the radiator), de lidding the CPU, or under clocking/under volting