I Had the headphones for almost 3 weeks before purchasing the cable. The headphones were pretty much broken in using the stock cable. Look I'm not saying the cable upgrade made these headphone sound like the HE-500s or Audez. What I a saying is for me they're were worth the money. High-end cable issues are what make non-audiophiles roll their eyes and make out out the be obsessive money wasting fools. Even today they remain controversial. Most cable manufactures offer money back guarantees so there's really not risk in auditioning the products. Do you know Transparent Audio make speaker cables that cost $40,000? That's 40 large! When these cables are ordered the whole plant shuts down and it can still take up to a week to finish the order. Wilson Audio and Rockport Technologies make speakers that cost hundreds of thousands of dollars and both companies recommend Transparent cables.
My point is cables are big time **** and improve the sound of most components. Of course there are rip-offs out there as well.
But with a little bit more money than what you spent on the HE-400 and cable, you could have gotten a HE-500 which would have been a much bigger improvement in sound than even the best cables.