The 69xx series of cards only has one DVI out and 5 DP outs ....
I thought the HIS HD 6990 only had 4 miniDP connectors?
Anyway, perhaps you should try connecting the Samsungs using the DP adapters and the Hazro with the DVI connection.
I'm not sure how your setup would work in Eyefinity as I thought all the monitors had to operate at the same resolution. Perhaps I'm wrong?
It works fine over DP to dual link dvi, as it should (apple model on an m18x). Passive/active single links won't work.