Gonna be buying a GTX 1070 very soon, and I noticed that the graphics card required an 8 pin, or 6+2 connector, and I was wondering what ($30-40) power supplies had either an 8 pin, or 6+2 connector.
efficiency is meaningless when talking about PSU quality and it is really last to look at.
As well as many PSUs from brands like corsair VS, Antec BP and many others are total crap.
There simply aren't any PSUs for $40 or less I would trust to run a 1070 reliably. If you post the full system specs I can make a few suggestions for a reliable budget unit to power the system.