A quality 700-750W capable to run any single gpu setup to date and is recommended as well. Such as above given links. For single 980Ti, 850W is a bit more unless you're getting a cheap deal.You need a quality unit having quality component inside, and not ratings. In other perspective, SILVER, GOLD, and PLATINUM offers some high quality components, not every unit, but manufacturer behind the power supply justify the quality builds, Like Sunflower, Flextronics, FSP, Seasonic. On the other hand, Corsair, thermaltake, Cooler Master are not manufacturer, they only brands their product (PSU). How would you know the manufacturer details of specific model? Just go and read specific model reviews on jhonnyguru or HardOCP then make your purchase. That will give an idea which PSU is capable of what, especially for long run purpose.
