Please have look at this Sotm SMS-200 thread. Some potential improvements for your setup are to use a powered usb drive and a low noise power source (the one supplied had a crappy Aus adpator as well!). Also remove wifi dongle and use a network cable.
For a long, long time, I had the same misconception. I had a laptop running Foobar2000 to my DAC, using a spare generic usb cable. 1's and 0's in a true digital stream - that is all that is needed! And a cable is cable.
Unfortunately, jitter and noise affects the digital stream, which in turn impacts the music production. Since getting the SMS-200, a mid priced usb cable and a Gieseler PSU, music has improved markedly.