If the second rig is cheaper, get that instead along with an EVGA 1000W P2 PSU, which is 80Plus Platinum efficiency.
Otherwise, just get the Biostar but try to get a G2 PSU at least.

Do NOT get the G1 in any case, considerably lower quality than G2/G3.
1000W should be enough for 6-7 GTX 1070s.

EDIT: You could also ditch one stick of the RAM and go with 4GB to lower costs.