My benchies, have images if you want
Windows Basic Theme with MSI AB running. CCC Default
Windows Aero with MSI AB + Hwinfo running
Fraps too let me score 9840.
With CCC = Tess Disabled. 11k+

lol, I know this is irrelevant
AND
Graphics score and Physics score alone don't show the true picture of the kind of improvement you would get in real world games.
I know 3D Mark isn't a 100% representation for real world gaming, but their overall score increases with overclock are very close to the kind of real world performance increase you can expect with the given overclock, at least very often.
With a stock card sub 8kish I went to nearly 10k once overclocked. That is approximately the kind of improvement I see in my games as well. But the graphics scores and physics scores are relatively more biased and rise or decrease relatively very quickly, real world gaming isn't as quick in increase/decrease.
It is the overall P score which is a better representative of performance, and the individual scores are more for troubleshooting and other purposes IMO, and of course to benchmark as well
Even if you do get 13k or so, that is just 30% more than what I get. Even if you do get 30% more FPS in games, a single card will run it better because it will be at least as smooth if not smoother, and won't have any MS etc, and again no CF hassles, and will scale better where CF isn't supported.
To actually make CF worth it, anything below a 50% performance increase isn't worth it. Because 50% more FPS means that if you were sub 40 FPS you will get near 60 and with CF you need at least 60 FPS for smoothness, while 45-55 FPS may work out with single GPUs.
IMO Getting a single 670 7970 680 is a far better deal compared to 7850 CF assuimng the price is similar. Your games will be smoother, there won't be any MS, no waiting for profiles, guaranteed performance in all games, and less driver hassles. These reasons make loosing 20%+ performance worth it especially when your higher FPS are usually not as smooth either, except in some occasional cases.
You do need to consider the fact that if you considered 40 FPS playable with a single GPU, you will need at least 60 FPS with a dual GPU. And you will still get MS no matter how high the FPS. If you are able to play above 60 FPS, performance will be better (not hugely though) compared to 40s/low 50s of a single GPU, however otherwise the real world experience would be even worse once you switch off Fraps and actually feel the smoothness.
So I wouldn't go CF for anything less than 7950 high OC CF, and I wouldn't do that if the total setup costs an equivalent of sub $700 of USA.