I just had a quick listen between the two players with Fidue A83. X2 is smoother warmer (as in bassier) and less engaging than Alien, more relaxed or laid back, maybe a touch rolled off in the highs. This probably explains why I'm having such good results with the overly cool analytical H-300 hybrid. This also means X2' isn't quite as detailed, but on a technical standpoint X2 isn't really far behind in instrument separation and maybe even edge out on soundstage width as you see me keep mentioning these as strong points. It actually pairs really well with A83 similar to H-300. I think if you're looking to replace Alien for $55 that's not going to happen as we know that unit performs terribly high for its price. If however, you're like me always looking to mix n match tonality on that quest for synergy between IEM and DAP then X2 is going to have a place for you. For example, my H-300 has just found a new long time partner with X2. (I will leave them together because their tone sits well) I've also noticed X2 has a relay switch like found on common amps and iBasso units, that click you hear on start up switching the amp section on/off. For those who don't know what this means bassically there's no loud pop on start up because this relay switch inside X2 prevents any current reaching the IEMs.