I'd normally say that an i7 4790K would be overkill for a game like Fallout 4, but I have an i7 4790K, along with a GTX980, and I've experienced significant slowdowns while travelling through the most intricate urban areas so I can't really recommend much, since it's obvious the game has some optimization issues, but it's not clear to me whether the team at Bethesda plans to solve them. As far as I know, all that has been released for the game is a single patch that fixed some quests and a problem related to the Launcher, they took their time to release that, so there's no telling when we might expect those performance oriented fixes. Furthermore, I've read Radeon cards seem to have issues with Tessellation and they offer no support for GameWorks nor PhysX features (obviously). ATI technologies, like TressFX, are opensource while NVIDIA ones are closed, which means that the latter will always have the opportunity to implement performance improvements over new Radeon's features while the former can't even afford compatibility with the more advanced closed-source offerings of its competitor. It's obvious NVIDIA are the real villains here, but that doesn't change the fact that they offer a better package overall. Just sayin'.