Did you read the thread? Cinebench is completely meaningless.
The benchmark is heavily CPU bound, AMD drivers have less CPU overhead compared to Nvidia, so your 5870 will outperform every single Nvidia card you can buy, simple as that.
Have a look here:
http://www.tonymacx86.com/graphics/177227-graphics-testing-benchmarking-chart-4.html#post1158102
Scores are perfectly proportional to CPU clock speed when OC'ing but doesn't change notably when upgrading GPU.
The thing you missed is that this completely irrelevant to other applications/games. A GTX 970 will easily outperform your 5870 in gaming or GPGPU applications, just not in that stupid benchmark.