I recently upgraded my mobo and CPU to a system that fully supports using PCIe 3.0. (My old mobo could I think, but the 2500k could not) Anyways, other than a general speed increase in the computer will the 780 see any benefit from a 3.0 compared to a 2.0? Thanks in advance.
Here, take a look at HH review here in guru3d : http://www.guru3d.com/articles_pages/pci_express_scaling_game_performance_analysis_review,1.html
the difference between PCIe 2.0 and 3.0 is big for especial tests as memory read and write (AIDA64 GPGPU); vertex shader simple (3DMark 05 and 06) (and maybe high polygon count at 1 light (3DMark2001SE)).
Nothing that matters, no. I've upgraded to PCIe 3.0 two times already, temporarily , and there was no speed increase whatsoever in games. It's a good thing to have for SLI or CF, but doesn't matter at all for single cards still.
It very much depends on the game. During a benchmark comparison thread in Rfactor2 racing simulation, I found out (purely by accident) that PCI-e 3.0 gave a consistent 10-18% increase in that title over PCI-e 2.0. It also brought additional 'smoothness' when used in Assetto Corsa. As was said above, most other titles will not benefit.
Single gpus there is not much difference but with dual gpus i saw the increase. Especially with R9 290x crossfire.