You can try the RME and listen, and this is the best way.Thanks for your reply!
Would you consider a RME Digiface a good-enough converter to put between a laptop and the DAC X7 ?
The two-second delay and lack of drivers for Win10 don't encourage me to use it via USB.
Other question: do you use the power cable coming with the unit, or did you replace it? It looks cheap.
The stock power supply is a switching power supply and weak, and I replaced it with a linear one with enough power.
In some case the same switching power supply with enough power which is the same voltage with more than 2 amps for example, is an inexpensive solution.
You may order this cheap one for giving a try.
I chose TeraDak DC-30W 12V/1.5A FPGA Linear Power Supply.