Still have my X3 back in the day, during the early days of Fiio. Hell I still have their E3 amplifier that took a AAA battery. Fiio came a long long way indeed. They matured like fine wine.
You know the FD5 really does capture the essence, the emotion of music. Sure there are better technical performers but at my age, with the experience I have, I think I have shifted more towards finding that signature or flavor rather than cold hard specs or features. Yeah I probably won't need an upgrade for a long, long time....