I really hate to say it, but cables can make a difference if your system is revealing enough...and I'm not talking mid fi HE-500 stuff. At least something like a LCD-3 on a $10,000 rig (NAD+Luxman) I've heard, there is a difference between the stock cable and my upgraded HPL silver and Norse copper.
Although HE-500 on a Emotiva might not yield that. I certainly didn't feel much. Although the stock HE-500 cable was a pain in the ass to deal with physically.
IMO, at the most a headphone cable will form a low pass filter and supress high frequencies. If the capcitance in the cable forms a frequency corner in the RF, no human being is going to hear it, uber hifi or low fi, wont' make a difference. The amount of capacitance required at headphone impedances to intrude into the audio spectrum is rather large for such cables. You would have to find and purchase a really bad cable for this to happen.
Edited by StanD - 2/28/14 at 10:15am