Ok I will order 6 sapphire rx480 nitro 8giga cards. They are better for tweaking yes? Good cooling... With these I safely get 740 hash and sub 800 w in total yes?
Yes. They are good cards, with the best (lenient) mosfets and good cooling. They didnt go cheap like Gigabyte or Powercolor. But remember you may still need to tweak you bios / strap timings to run it efficiently.