I hope you're still monitoring this thread. Today my nearly four-month-old HE-500 developed a problem with the left driver. It's been fine, including yesterday, but now only outputs approximately %25 - %50. I've confirmed it's the HE-500 and not anything else in various audio chains, in which two other headphones perform perfectly.
While I've contacted your customer service via the form at head-direct.com, I thought I'd ask a question here.
Because I'd be returning the HE-500 for replacement, not repair, would it be possible to exchange it for the HE-560, paying the $300 difference. I think this is a reasonable request. If you're reading this, please let me know.