use auto logon, ok its not safe that way to use centos 7.3 but there is a bug in the GDM greeter , i fixed by this way.
install the driver, not reboot yet go typ in Terminal = as ROOT
and add these 2 lines
# GDM configuration storage
AutomaticLogin=david <----- log on name !!!
Now reboot and hopefully you a go !! AMD RX would work full now.
rpm -qa | grep amdgpu-pro
I have the same problem (Radeon RX 460 black screen).
My system is a fresh install of Ubuntu 16.04 with XFCE desktop and the last vesion of AMD driver installed (amdgpu-pro-16.50-362463). It doesn't work with and without autologon, I've the same black screen.
My motherboard ASRock N68-GS3 UCC with an AMD Athlon II X3 450 (with the 4th core unlocked) and 8 GB RAM
Any suggestions for Ubuntu?