Some clarification :
I assume this is a Chord Qutest, not Quest. I have the original Hugo. Nice DACs.
Is the ifi an original iUSB or a iUSB3.0? Those devices are regenerators, not chargers. Are you matching the usb of the PC and the usb of the ifi? Plugging a usb 2 device into a usb 3 port or vice versa can sometimes lead to problems. I am not sure if the Qutest works equally well with usb 2 and usb 3.
The Qutest uses a wall wart power supply. I assume you are using that. You cannot power the Qutest via the usb.
I assume the Qutest works correctly without the ifi installed.
You can test with WASAPI rather than the Chord ASIO driver. The only thing that does not support in DSD 512. WASAPI will use DoP for DSD, whereas Asio will use native sample rates.
Once you get the ifi working, it would be interesting to know if you hear a difference using it. The Qutest usb is galvanically isolated so the comparable features of the ifi should not matter. The signal could be improved by being regenerated by the ifi, but the Chord should be pretty good with anything other than a very poor usb signal.