Using 3DMark 06 to show that 3930 with 2 GTX570s is faster than a 2600k system is pointless since 3dMark06 is a very CPU limited, and not just a GPU limited benchmark. Also, 3dMark 06 performance has nothing to do with real world gaming performance.
Secondly, look at your 3dMark 11 scores, the GT1-GT4 gaming benchmarks are all faster on 3x GTX570 GPUs,which indicates that a 2600k system with 3x GTX570s is faster in games than a 3930 with 2x GTX570s (and this is what was supposed to happen anyway). The overall score is meaningless since its adding the CPU scores (Physics), making it useless for measuring overall performance in games.
Try running some games and you'll see the 2600k on Z68 with 3x GTX570s will destroy 3930K with 2x GTX570s in
ANY GAME. So if you are only building a system strictly for games, 3x GTX570s on Z68 even with PCIe being limited to 8x/8x/8x is going to stomp all over the X79 platform with 2 of the same GPUs.
It's already been shown 100x that PCIe 2.0 8x is NOT a limitation for graphics performance by more than 2-3%.
So now, your assertion that 3930 with 2 GPUs is better than 2600k with 3 GPUs (of similar performance level) is incorrect.
Since we already know that Z68 board with an NF200 chip
does not have a significant PCIe bottleneck for running even 3x GTX580s in SLI, the only way for your argument to be true is if the CPU advantage of the 3930K is MORE than the performance advantage of adding a 3rd GTX570.
Show gaming benchmarks to prove this. 3dMark is a waste of time.