There were 3 things that helped with my silent PC.
1. PSU
My old Thermaltake had the fans run all the time. I replaced it with a Corsair HX (RX, HX, and AX will work). Even though it's not passive I never heard the fan turn on with my Corsair PSU and my GTX 970 and CPU running at full load, if the fan does turn on, it's at 10db which I think is inaudible.
2. CPU cooler
I had a Cooler Master Hyper 212 EVO, the stock fan was too loud so I swapped it with a Noctua NF-F12 and it's silent even at 50% fan speed.
3. GPU
I have the lowest Zotac GTX 970, and I can't hear the fans at 30% idle speed, I used MSI Afterburner or equivalent programs and messed around with the fan speeds, no noise at idle and expected noise at load, but not excessive.
When you boot up your pc in the morning keep and ear open during boot and listen for the loudest hardware. For me right now I am using the Hyper 212 EVO stock fan as a case fan, it's the loudest, next is my HDD.