After 21 years of Intel builds (and many years of apple machines before that!), I built my first AMD machine.
I chose the 3600x because I ordered it on release day, and just kinda picked the 3600x at the price range I wanted to spend. I realize I could have save money by buying the 3600, and overclocking... but I haven't bothered to overclock a CPU since the overclocking my Pentium 4 Northwood 1.6 to 2.4ghz :)
I got the 1660 ti on 20% sale through Newegg, but otherwise bought everything standard prices.
I wanted to make it pretty quiet. Hence the Noctua fans, with the two 1700 RPM fans as output on top and back, and two 1300 RPM fans as input in front. I even replaced the standard fan on the Cooler Master 212 with a Noctua NF-F12 PWM chromax. I have no ability to record decibels, but its pretty quiet machine.