I did some more checking and it seems to be the particular combination of HDMI and DisplayPort that causes the crash.
I hooked up my old Samsung via DVI and left the DisplayPort connected. Sleep and woke perfectly.
Hooked up all 3 - DisplayPort, HDMI, and DVI. Sleep and woke perfectly.
Put the HDMI and Displayport monitors back and hang on wake. It seems that the HDMI comes on, then DisplayPort comes back on (the monitor wakes up) and then the signal is lost.
Any ideas? Or how to get this in front of AMD?