Yes, it's enabled. I have tried everything I can think of, and now I'm wondering if it's my video card. Thinking about picking up a newer video card from BestBuy today.
According to the Specs section here, the 6950 supports a maximum resolution of 2560x1600, which I find quite surprising. I had to double check my card too, but it supports 4K.
My monitor is supposed to arrive tomorrow and I'm planning to keep my Radeon 7870 (Tahiti LE) at least until we see the new cards from AMD in February/March. If any of the current rumors pan out, the R9 380X will have about 15% better performance than the Maxwell GTX 980 and be cheaper to boot. But pigs may yet fly...
The last three upgrade cycles, I've wanted to switch back to Nvidia because I could actually use CUDA for some of the work I do, but I always end up with AMD for price/performance reasons. A pity that OpenCL isn't as widely supported.