I was about to ask you to test 68XX cards with DP on 4K but the Seiki does't have a DP input. :(:(
New Radeons supposedly should be better, because they have beefier ROPs.
I think buying the Seiki was a poor choice. It is not even a good TV, and 4K @ 30 Hz does not allow visual confirmation that games actually run well at that resolution.
If one just wants to benchmark gaming at 3840x2160 resolution, just connect 4 identical 1080p monitors to the graphics card. This is possible with all recent high-end cards from AMD (yes, no need for 3rd monitor to connect via DisplayPort in this case) and NVidia.
And now Dell has listed the UP2414Q 24" 4K monitor on its website, which I guess will be more affordable than the other monitors which display 4K @ 60 Hz.
Next year, we'll see more affordable 4K monitors for PC gaming and graphics hit in the holiday shopping season along with 4K TVs all sporting HDMI 2.0. The panels being made are all 10-bit so there won't be a premium for 10-bit displays anymore though getting 10-bit color is still going to be a pain in the ass since it's not the standard yet. HEVC decoding is still a long way off from being put into the hardware for GPU video decoding but h.264 works just fine at 4K resolution and works with many current GPUs.
You wrote that the Gallium3D driver can not be used for games but what about normal desktop usage? Would that work? Was the computer sluggish the few minutes before you installed fglrx? And what about the resolution, did it set it up correctly?
Thank you very much for your answer