Wont be loud, but itll be slighty louder than a system which was just air cooled with all fans at 6-800rpm in both scenarios. Mainly due to the hum of the pump (which cannot be slowed down on the AIO units).
Did you not look at the basic EK/XSPC kits, they are actually really easy to put togethor. Takes time, but its not difficult, then after the first time its easy as pie. On the noise front, depending on the pump it can be a little quieter, but of course better performance. These loops let you either undervolt pumps, or yu can even get PWM ones that change speed with CPU temp.
Heres my rig with an EK 120 Kit, CPU is 3960X at 4.8Ghz. Case is Lian Li PC-354B,
These EK DCP pumps are a bit rubbish though, they have a slight buzzing noise, been through 2 of them, both same crap. Performance is few degres better than the H80i i had before, but these rad fans are at 1600rpm (under stress test) and H80i was 2400rpm.
Another option for a case is the Silverstone TJ08E.