At 1080p we find that Fallout 4 in all of its ultra-quality glory isn't that dependent on the GPU. Mid-range cards of years ago are able to deliver playable performance, albeit just. For instance, HD 7870 spat out 43fps and never dipped below 34fps while the old GTX 660 Ti was even more impressive with an average of 49fps and a minimum of 38fps.
The modern budget graphics cards such as the GTX 950 provided very playable performance with an average of 51fps. The mid-range contenders such as the GTX 960 and R9 380 offered solid performance as well, though the GTX 960 was noticeably faster with an average of 63fps opposed to 55fps.