GPU for rookie

Hello guys, I’m a complete amature in blender and im using render/cycles with CPU i5-6600. Now i decide to buy GPU.

Any advice what I should buy? Some new GTX 1060? or maybe its no worth and buy any older card like gtx970 ?

if decide buy 1060 6gb? which one get. many cards have difrent clock speed?

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.