I've had my SR15 for about two weeks. Here are a few sound impressions: Until yesterday I was listening single ended using my Audeze iSine 20s and Shure SE530s. My impression upon first firing up the SR15 was that it sounded thin. I wasn't certain I had made a good purchase decision. After playing it a couple hours, it sounded fuller and really opened up. The change was not insignificant. No more uncertainty. The iSines sounded good single ended, as did the SE530s. Both were full, rich and unconstrained. Yesterday I received my new, balanced Reference Silver headphone cables from Lavricables. To say I was blown away by the improvement in sound from my iSines would be an understatement. It's a whole new ballgame! The 20s sound natural, punchy, full, dynamic and spacious. I would not have believed the difference would be so great. Tomorrow I will receive the Astell&Kern Beyerdynamic Special Edition AK T5P 2nd Generation headphones I ordered earlier this week. I plan to use them with both the SR15 and my Bottlehead Mainline amp. I'll report back once I've had a chance to give them a good listen.