Will a quality USB cable make a difference....

I have recently bought a Mach2 mini and an Empiricle Off Ramp 4(ultraclocks, Hynes Regulator). This is my first try at computer audio. These were put into my system inplace of my transport a Krell MD10. The computer system (Pure Music) beat my transport and I was quite happy with the results. I was using a belkin gold usb cable when I saw an RSA Enopias come up for sale here on AG. I did not expect much of a difference if any at all. Empiricle advises cables before the off ramp matter little. That being said I sometimes like to try things for myself. I felt I could resell the cable and not loose anything at the price offered. After installing the cable I noticed how much more extension the bass had. The sound stage was larger as well. The cable made a very nice improvement to my system. The cable I bought has no power. Perhaps that's the reason for the improvement. Anyway I will be keeping the cable. These are my findings YMMV.

The rest of my equipment:
MIT MA X Digital Coax
SFD2 MkIII 24/96
MIT MA Proline
KCT
MIT MA Proline
FPB 600
MIT Magnum MA BiWire
Andra II
RSA Dmitri
RSA HZ Crown Jewel (PC)
PSA AC12 (DAC)
PSA AC12 (PRE)
MIT Oracle AC2 (AMP)

Perhaps it depends on the components in the system and their configuration as to whether the USB cable makes an audible difference or not.

I have a standard commercial USB cable, a Belden Gold and a Nordost Blue Heaven (on loan). While I believe the Belden Gold is an improvement over the commercial cable I haven't heard a difference between the Belden and Nordost USB cables. I have a high end headphone system as follows:

Computer > lossless > iTunes > USB > Belden/Nordost > Cary Xciter DAC > Nordost Blue Heaven RCA/Blue Jeans RCA/DIY RCA > three channel beta22 amp with sigma22 power supply/Woo WA6SE > Senn HD800

I'm also using a Nordost power cord on the amps and Jellyfish PC on the DAC. I have found better results with the PCs and ICs than I have found using a pricier USB above the level of the Belden Gold.

Only difference I found was the conector's firm fit on the computer side. No other disernable difference to my ear. Not sorry that I spent $100 for the cable for that reason though.

I had a top audio guy in the industry tell me something interesting when I asked him this very question. He told me to use a Belkin Pro or Gold series USB cable; that's what's being used in the studios when the music is recorded, engineered etc. I can't say that I've experimented with USB cables myself, but it's certainly an interesting perspective.