Latest drivers? Is that blockchain drivers or normal gaming drivers?
These drivers are blockchain one:
http://support.amd.com/en-us/kb-articles/Pages/Radeon-Software-Crimson-ReLive-Edition-Beta-for-Blockchain-Compute-Release-Notes.aspx

I have a friend with exactly the same parts as your on rig 2(cards, mobo and psu). He modded his bios and have 30 Mh/s eth and 900 decred in dual mining.
I can ask him for the bios if you want.