My best friend loves his new nVidia GTX 980ti, but I seriously doubt you will get one small enough to fit in a mini-itx case, AND keep it cool. His gets up to 85C playing GTA V in a Full Size EATX tower.
970 should do near ultra at 1080p.
If you are willing to wait I would, to see the size, cooling and benchmarks of the NANO, especially after seeing how well the non-x Fury does.