I am looking to install an ASUS Xonar Essence STX sound card, and I need to know how to connect it to my power supply. Here is a picture of the power connector slot (4-pin Molex, I believe):
My power supply (Seasonic M12II 650W 80Plus Bronze Power Supply) has a number of different slots for cables, pictured below:
The STX sound card is a PCI Express device - should I use the PCIe slot on the Power Supply? Should I use 6-pins, or 8-pins? Please let me know which power cable I need (an image or link would be greatly appreciated).
Thank you.

My power supply (Seasonic M12II 650W 80Plus Bronze Power Supply) has a number of different slots for cables, pictured below:


The STX sound card is a PCI Express device - should I use the PCIe slot on the Power Supply? Should I use 6-pins, or 8-pins? Please let me know which power cable I need (an image or link would be greatly appreciated).
Thank you.