6* SAPPHIRE VGA PCIE16 RX 580 Pulse 8GB - I'd go with this choice.
It will be easy enough to get 28+ Mh/s per card with ETH. 320€ - 20% off is fair price.

Couple weeks ago I got my ASUS Radeon RX 580 8GB (Samsung) cards by 300€ each and so happy with it, from stock it gives 25.5 eth + 800 dcr.
I'd buy more, but cannot find these cards cheaper than 375€.