Antec is a normal brand and not a premium one, if you want to have 6 cards go for Corsair HX1200i and if you want 8 cards go for the EVGA G2 1500 watt PSU which has 8 , 6+2 pin PCIE cables for all your needs.
It is always better to start with a low number of cards to test the waters, usually 3-4 and then you can add as you like. This is because with lower number of cards is easier to troubleshoot.
How will a 1500 watt psu alone power 8 high power gpus ? I like Antec because its service is good. I recently got two new PSUs in exchange for two dead PSU
I am talking about 8 x Radeon RX series cards , it can support 8 of them without problem as after a good bios modification and undervolting it will easy power 8 of these cards.
If you want to go with the Rx Vega then it can support up to six of them with bios mod and undervolting.