I'm not sure that this will have a great value if you're using top end GPUs like Titans or 7990s, where the difference in FPS between CPUs is in the imperceptible range: a 10fps difference between 70 - 80 won't affect many people. If you were to use a more mid-range GPU like a single 660ti on the machines you'd see the performance gaps (if there were any, I'm not saying there are enormous differences) in a fairer way.
Still nice idea :D

