i use a gtx 970 and it works great. i hear the new 10 series still has some bugs left to iron out. the 9 series has been supported since 2.73. i find it helpful to have flexibility to what version you use.
if you go with a 10 series, your stuck at 2.78a and up.
i hear the 1060 is faster then the 970, and the 1070 is a beast of a thing. the 980 would be a big step up from the 970.