Hi Alex,

I just tested acpi=off independently and not amdgpu.dpm=0 independently. 

In regards to the other user, yes he had the exact same PCI resource issues as
me, what I'm curious to find out though, is when he passed in PCI=noacpi and
was able to get the card initialized if those same PCI resource issues are
present.  My hunch is that they are still present AND the card was able to
initialize, but I'd be anxious to see.

I've also asked him to test out amdgpu.dpm=0 independently and report back. 
Hopefully you're onto something here!

Rob