Seems like Sound Blaster Recon 3Di improves the audio quality by noticeable margin. It improved treble and bass while maintaining good highs and mids, my HD 598 SR sounds sonic clear on my alienware m17x r4 than Samsung S7 edge or Asus Xonar DX sound card.

I have same question too. Did you found your answer, it's been 4 years :)

I think amazon is safer than ebay for selling genuine products. Any other good online stores that sell genuine Sennheisers?

Any stores selling replacement hinge parts? What could be the price of repair? I bought mine from amazon and shipped to Mongolia using 3rd party freight forwarder, and warranty is expired.