So here is my .02 thoughts worth on the X3. I have both the X3 and the Ibasso DX50.. I truly enjoy both for their strengths in sound. I noticed that the X3 is the more musical in presentation in sound, deeper fuller mids and bass vs the more neutral balanced wider stage on the DX50.
This being said. I also noticed more neutral phones synergizing better on the X3 more so than the DX50..So based on that info if any of you guys are wondering what Dap to get. I would base it on what phones you guys own more so than anything. Both have a great sound but will synergize much more so with phones that have the opposite in sound.
The funny thing is I can see many guys wanting more "neutrality" in their sound that will probably go with the DX50 but it will be the X3 that will synergize much better than the DX50 using neutral phones.
Using colored phones on the X3 is a no no by the way.. Will add a bit too much coloration to the sound. That is where the DX50 shines. Either way both are excellent but know that opposites attract when it comes to both these players.
I certainly agree with your assessment regarding the X.3. However, I don't think using it with warm headphones is a no-no. Obviously this is a subjective topic, but I thoroughly enjoy mine with my BA 200s and TPeos H200, both of which have a warm tilt to varying degrees.