I currently have an AMD FX8350 (oc 4.2) coming soon from a friend, and wondering if a gtx 780 would bottleneck it? I mainly play skyrim (heavily modded), the witcher 2,and some others etc. C:
No. The CPU and motherboard bandwidth is more than sufficient for a single 780. It's a really good card for mods et cetera.
What you may have to concern yourself with is your display. A 1080p 60Hz display will bottleneck a 780. I max out my 1440p panel with a 780 whilst playing a heavily modded Skyrim. The FPS doesn't fall below my monitor refresh rate, which effectively acts like a cap on maximum FPS. If I can do that at 1440p with a 780, then a 780 is too much card for 1080p, in my opinion.
At 1080p an overclocked 7950 (with that 3GB of Vram sweet spot) compares to an overclocked GTX 770. I would recommend a good 7950 for that resolution. You can buy two good 7950s for the price of a 780, which is something to consider. Skyrim happens to be more CPU dependent, rather than GPU dependent. The 8350 is a good CPU.