Hmm it's almost $300 for the upgrade to Intel. Also, don't upgrade from 6300 to 8350, that's probably not going to change any numbers.
Have you considered overclocking the 6300?
You could probably find benchmarks, but if you overclock the 6300 to the same speed as the 8350, I bet the gaming performance will be about identical, so it's a total waste to upgrade to the AMD chip unless you can do some video editing.
Now is it worth $300 for the upgraded motherboard and Intel CPU? If I were you, I'd find benchmarks for those specific games, and see what is the FPS increase you'd get.
But keep in mind, at triple-screen gaming, you may not reach the full theoretical speed available from the CPU, because the GPU will be holding you back.
Ultimately, if you are going to be held back to lower FPS anyway by the graphics card, you could argue that the faster CPU would simply go to waste.
So, based on all the above, you should overclock your existing CPU, buy a 2nd video card for crossfire, and that will probably get you faster FPS because the Intel chip wouldn't be able to reach its full potential under a single video card trying to run eyefinity.
PS: out of curiosity, is there a specific scenario where you find your CPU is too slow? OR are you just suffering from low FPS while playing eyefinity resolutions now?