Got my hands on 12 of those for quite a low price: http://www.sapphiretech.com/productdetial.asp?pid=77B48A1E-9FCB-4F19-BC2D-17C3087E4852 they use 8pins for power

And I got those PSUs at home:

1x https://www.evga.com/products/product.aspx?pn=220-P2-1600-X1

2x https://www.evga.com/products/product.aspx?pn=120-G2-1000-XR

Im planning on getting 6pin powered risers aswell or some molex ones if needed

All those PSUs give me a total of 17 6Pin Ports and 21 8Pin Ports (although some of the 6pin ones are labeled SATA while some are labeled Perif, not sure if those are still compatible)

So i need to feed:

12x 8pins for the GPUs
12x 6pins for the Risers

Now I dont't know which would be the smartest way of getting the cabling done, and which additional cables i should get.
Can i power a riser + a GPU on one cable? I basically need to know on how many and wich cables i should split up which components.

Hope you guys can help me out, cheers!