Keep in mind that since yesterday the GTX 1060 3GB cannot mine anymore Ethereum due to DAG 177 difficulty increase so if you have not yet bought your cards do not buy one of these.
DAG won't reach 3gb until a year from now, if you are unable to mine then you're getting screwed by your OS (win 10 i'm guessing?) There is no reason not to use win 7 or linux on a 1060 rig.
Also DAG size is unrelated to difficulty.