Hi Synack,
Yes, the 8pin connector is installed. With the Seasonic power supply there's actually two 8pin connectors. I've tried both and measured the voltage across the pins (I wondered if there was a fault in the power) and all the pairs show 12v.
The reason for my question regarding PCI cards on a Z77 is I read that the Z77 chipset doesn't actually support PCI (just PCIe etc) and that a bridging chip is used (asmedia 1083). So wondered if there was an issue and if anyone had one actually working.