I have several Furutech cables and they are very high quality cables. I do hear an improvement, but not sure if I could pick out the Furutech from the original in a blind test (haven't tried). Normally when I have the same volume level on the amp and just switch cable it's like the OCC cable sound fuller and more precise (almost like the volume level is a little higher with the OCC cable). I must say though that the improvement is very subtle and probably not worth the price of these cable because they are very expensive. Most of the time I buy them because I need shorter length like 1.3 meters - don't have any use for 3 meter cable when listening to music at my desktop.
If you are using usb dac's as a source I think you would get better benefit of trying out products like Audioquest Jitterbug, USB Regen, Ifi iPurifier 2, Wyred4Sound Recovery (especially if the dac is solely usb-powered).
Cables can provide perhaps 2-3% improvement, where these usb-filters can provide perhaps 5-10%. Still the improvement is at most subtle and maybe not worth investing in. Many companies have great return policies so it can be worth to try it out at least.