Thanks for the responses.
However, when the specs list the #6+2 PCI-e connectors, I thought it was referring to slots in the PSU itself, not the number of cables.
The HX750i has 5 slots which it labels "6+2 PCI-E and 4+4 CPU". Can the 4+4 CPU slots be used as PCI-e for the 2 SLI GPUs which will need 4?