Upgraded my second PC from FX8350 to Ryzen 5 3600 with a B450 Tomahawk Max. 
Before it was really struggling to play VR on this PC. Not so much the CPU and the 390X but the ancient motherboard was getting crazy hot trying to handle all the throughput I guess. 
Underclocked to 3.45 ghz and max power reduced to 55w instead of the default 68w, my Mixed Reality headset is actually working pretty great. Not even the 390x is getting as hot anymore (it really shouldn't since it has a huge Accelero Extreme IV cooler on it and its so big it slightly bends the board. Its getting replaced with a 5700XT next month because it makes me paranoid)
Playing Beat Saber and Gorn, the CPU didn't exceed 50 degrees, and the GPU didn't go past 55 either. 
It's really nice since the kitchen is the only place in the house with suitable room for Mixed Reality. Less chance of slapping ceiling fans and walking into walls.