GTX 1070 Graphics card vs Dell 4K monitor?

Should work OK. The Asus ROG Strix handles Rise of Tomb Raider at 39 FPS, which if you think about it, isn't too bad. If you want over 40 FPS, then you might want a 1080 or aTitan X, but those are very pricey cards. I'm planning on getting the Asus myself, but there are other good brands out there too. Guru3d has reviews of the cards, as does Tom's Hardware.