I use this afofrdable one - already makes a difference - might be enough for your system too...
Spending much more might not get you significant upgrade:
http://www.amazon.com/Belkin-F3U133V-06-GLD-6-Foot-Hi-Speed-Cable/dp/B000621N26/ref=sr_1_2?s=electronics&ie=UTF8&qid=1352266755&sr=1-2&keywords=belkin+usb+cable
Spending much more might not get you significant upgrade:
http://www.amazon.com/Belkin-F3U133V-06-GLD-6-Foot-Hi-Speed-Cable/dp/B000621N26/ref=sr_1_2?s=electronics&ie=UTF8&qid=1352266755&sr=1-2&keywords=belkin+usb+cable