Before you order any new Ram can you post a Speccy url for us please, details here
8GB modules do seem to be more problematic than the 4GB sticks, I cringe when I see people having computer issues and they only have a single 8GB stick of Ram as you know straight away that if the issue/s are ram related the person is going to be circa £125/$210 out of pocket after the initial loss and replacement costs.
http://speccy.pirifo...kCFg0tpx0J1zwgM
There's the URL. I've put my Kingston HyperX Red ram (2x8gb at 1600) back in as I've already returned the AMD ram. However while returning the AMD ram I did notice they actually sent me the wrong thing. I was just keen to get it unboxed and in the pc unwrapping it so I didn't notice until I removed it that it was "AMD Performance" not "AMD Gamer" so it COULD be that the performance series isn't tested on 990fx boards. But at this point I think i'm going to admit defeat and get 2 sets of 2x4 ram that are on the QVL.