I too love my dt 1380s have only had them around 6 months and have had zero problems maybe I just have the right shape head for these but I wear them almost daily sometimes as much as 8 hours a day and there still pretty comfy the sound quality is superb but I was wondering if it'd be worth getting a portable amp/dac running off a S9 for better sound stage with only a headphone jack could it be worth it. For the portability, price range, and personal tastes there really are none better.
To be honest, I say it's not worth it unless you have a line out. I have a cowon d3, which should have equal or better sq than S9, and double amping does not help. Sure, it's cleaner than double amping with a ipod, but double amping worsens the clarity and detail. But with a proper line out or audio out(ie. android or good dap), it is worth it to get a good portable amp/dac. For me, Sony E series>Fiio LOD>Leckerton UHA-6S.MKII pairs well with DT1350.