Good enough for what exactly?, we have no clue what kind of games you wana play, what type of rendering work, nor what resolution and refresh rate your monitor is.
I will give you an answer anyways, in my humble opinion the GTX 1070 is a very good 1080p gaming card. And can be a decent 1440p (as long as you lower some graphic settings).
Keep in mind that some games wiill require more GPU power than others, so my answer is a sort of a global idea of performance. Some games will run better than others.
And you need a decent PSU.