1. I'd go for some rx570 4g (or 8GB for 15-20$ more) - maybe 2 rigs with them - they will be mining crytpnight coins, there no need to buy RX 580 which is more expencive and have almost same performance.
2. Then 3 rigs with RX580 for ETH or dual mining
3. Then I'd take 2 rigs with NV1070ti - for other coins that loves nvidia cards, btx, zcoin, neoscrypt and others
I was thinking of the 580 since from what I picked up checking others' benchmarks it had better performance than the 570? And the price difference is kinda negligible.
I'm curious about the nVidias... to be honest from what I've searched it always looks like the 580 seems a better bet overall?
I wasn't really looking into many other coins as much as ETH.