Thanks, that's very helpful. I'm guessing RX 580 will do even a little better than 570.
The 580 is supposed to be about 10% better at Ethash, from what I understand. That depends greatly on the brand of memory and how you do in the "silicon lottery" (ie - some cards - even with the same memory - overclock better than others). My specific RX 570 (from Best Buy) is the XXX edition by XFX.
So it sounds like GTX isn't wrong if you're going to buy those as well but each is better for different coins.
Absolutely, it's just that specifically for Ethash coins the most recent models of the GTX 1060 - pretty much regardless of manufacturer, it seems - now come with crappy memory that dropped the hashrate from ~24 MH/s down to around 19 MH/s. Equihash mining - which is much less memory intensive - seems to be unaffected, so the superior performance of the Nvidia cards at this algorithm persists.
...If I can get a 25 mh/s rate for Etherium mining I would consider that a great start.
Then a stock RX 570 (as long as it has the dual BIOS feature /or/ you are willing to void your warranty modding the BIOS) should get you done. Like you, I'm starting off modestly with just 2 card rigs and I concluded that the RX 570 offered the best bang for the buck when it comes to Ethash coins; it was a much tougher decision for the NVIDIA rig, as I was really tempted to go with a single 1070 Ti to start, but some Asus dual fan ("white edition") 1060 3GB popped up on Newegg for $189.99 (after rebate, limit 2) so I pulled the trigger on 2 of them. That gets me around 20% more hashrate on Equihash for $70 less (yes, I am well aware of the density vs. $/hashrate tradeoffs, which is why choosing an NVIDIA card was so difficult).
