connectivity Question

I have a laptop connected to my Burson 160D using a cheap USB (1 coax in and 1 USB in) I have my CD player connected via coax. Here is my question: AM I better off buying a hi quality USB cable to connect laptop or should I spend the money getting a USB/coax converter and a good coax cable into my dac? Will either give me better results?
I would continue to use the USB for PC audio and the other input for your cd player. No real benefit of spending additional dollars on a USB to Spdif converter. It might ev en be a step backwards.