The card does not connect to the pci slot at all. It connects the the usb3 riser on the motherboard. Connected in this way the sound is on par with my existing pci usb3 card.
There is the option to add in the external power supply which is supplied and again I could not hear a difference. On testing I found the power supply to have an AC output of 5 volts not dc. This would insert noise. I changed this for the second output from my linear power supply and I can say that now this is an improvement over the old usb. Many usb chipsets in dacs take their power from the usb so making sure this supply is also filtered DC is a must. Now very happy with the results. Note red lead on your meter to the centre should be positive 5 volts if changing.