After testing the Sony ZX1 for some weeks I am very satisfied. The sound with the NAD Viso HP50 is spectacular. Especially well-recorded, acoustic Jazz like that on the ECM label (ALAC files). Just superb detail and soundstage. Only small gripe is the fact that I have to turn up the volume to near-max. Thought about a headphone amp like the Fiio E18 or E12 (the sony PHA-2 is too expensive). Would the Fiio maybe interfere with the sound characteristics of the zx1? Because I find them near-perfect (without any sound enhancements and with the stock player). Not sure I need the amp, but what I do need are good in-ears. I'm thinking about the Shure SE 425, maybe 535, but their >300 Euro price tag is a problem. Can anyone recommend the RHA MA-750 with the sony zx1? Or maybe the Philips Fidelio S1? I'm looking for clear, analytical, non-bassy earphones for less than 300 Euro.