Originally Posted by khyaris
Thanks for your detailled reply. I am also considering the Sony NWZ-15 over the fiio X1, since I have found it for 120€.
I would pair it with RHA ma750. Any opinion on this?
You are welcome. For facts like battery life, dimensions, file support and functionality please refer to the product page of the players. Let me give you a user's perspective on the sound and usability of the players.
Sound Quality wise, both are good and you won't find much difference. X1 has a better amp section that can drive hard-to-drive headphones and also has a clean output (does not hiss with very sensitive IEMs). Sony A15 has enough power to drive all the headphones that you currently own. In case you need to use with demanding headphones, you would need an additional amp. With super-sensitive IEMs Sony will have a background hiss that you would hear in a silent room when you pay close attention when no music is playing. But I don't think the MA750 will have the hiss. I have a Sennheiser IE80 which is more sensitive than the MA750 and I can hear a hiss in a silent environment.
Volume Cap on A15:
If you are getting the european version of the A15, I have read that it has a volume cap. It wont let you increase the volume beyond 40%. But I remember reading somewhere that this volume limit can be bypassed somehow. Be sure to ask in the Sony A10 thread here on head-fi and people will be happy to answer your question
UI and Navigation:
Fiio UI is pretty basic but I like it much except for having to navigate with the scroll wheel which feels tacky. Also I like Fiio's shortcuts and navigation. They have been hearing people's feedback and have been fixing issues with each firmware release. Sony's UI is very intuitive and you will master the navigation in a day. If you have owned any Sony Ericsson phones in the past, you will fell like you are in a familiar territory. Except for the Scroll wheel on the X1, both the players get my vote on the UI aspect.
Fiio's accessories ecosystem is pretty good and also can be kept under the budget. Although Sony's accessories are also easily available, it can be a little expensive. it has it's own proprietary walkman port and the corresponding cable.
Deciding between these two is a matter of preference or need and much less a decision of picking the better one. If you want a player that can drive some demanding headphones, and if you want a lot of manual controls, and you don't mind the weight and size, choose the Fiio X1. If you want to just play music on your IEM or easy to drive headphones and never care about making a lot of adjustments, choose the A15.
Why I chose Sony?:
I bought both the A15 and the Fiio X3ii so that I could compare both and keep the one I liked and return the other. Both cost the same here in the US: about $200. Although X3ii sounded slightly better and offered many more features and fidelity options than the A15, I ended up keeping the A15 for practical reasons. And also it came with the added advantage of internal memory, slim design, lightweight and long battery. One other reason that I chose Sony over the Fiio was that I saw a couple of members complaining about the scroll wheel of X3ii becoming unresponsive or acting funny after a few months of use. I wanted to avoid these complications.
Sorry for that long response. But I hope this helps you make the right decision.