You did not mention storage device in your post and a SSD is silent as can be.
This autumn I built both passively and actively cooled computers for home use, and the below is for my gaming, erh, essential work at home. It is the most quiet actively cooled powerful PC I've built.
With all power saving modes enabled in BIOS, as well as disabling some ASUS tasks (from the Task Scheduler), it is idling at about 40W and about 260W when running Furmark and Prime95.
The PSU fan is not running at all, with it located at the bottom of the case along with the SSD.
I use the CPU cooler (Noctua NH-C14) with just one fan, and had I known better I could used the second one as a fan case and saved some money.
The ASUS's Fan Expert2 is nice as it can control non-PWM fans and with it the Noctua CPU fan runs about 300 when idling, and the Noiseblocker fan case is off until about 50 C. When I turn on the case fan on I can not hear it, but as the temperatures are low I want less air inflow to reduce dust issues.
Sadly, the ASUS BIOS options have way too high minimum fan speeds, and using the low voltage adaptors from Noctua can result in too low fan speed, or at least I think so.
If I knew what I knew today I would skip the K version of the CPU.
Samsung 840 Pro 256GB
Kingston HyperX 16GB Kit 1600MHzNoctua NH-C14 Dual Fan Top-down CPU CoolerASUS GeForce GTX 670 DirectCU IINoiseblocker M12-S2Seasonic Platinum 660XP 660W
The case is my old Antec P180 first revision with some small mods like PCI shields having holes for ventilation and cutting away some plastic on the front ventilation filters (got the idea from a SPRC thread).