I think i'll go for 3x1060 + 1x1070 for the moment, i have 6 spot for GPU on my rig. Thanks for the help!

Do I need to avoid some models ?

I plan to buy this:
http://www.kfa2.com/kfa2/graphics-card/10-series/kfa2-geforcer-gtx-1070-oc-mini.html
 
http://www.kfa2.com/kfa2/graphics-card/10-series/kfa2-geforce-gtx-1060-oc-6gb.html