Thanks for the answers. RX 570 would be a good choice but I can't fin them easily (and maybe having more than 4gb RAM would be a good choice). What kind o performance can I have with a 6 x Gtx 1070 rig (in mh/s)?
Overclocking the memory, roughly the same as a 570/580 with modded bios.
Problem was 1070 were way more expensive than 580, but at the prices they're selling now, probabily not the case anymore.