All those things I've said are true. The X1 IS the culmination of all the things I've wanted in a headphone. There is absolutely no other headphone that has suited me as well as the X1 has. I'm doubtful anything else will.
As I've already mentioned, I'm selling because:
1. After having spent a few weeks away from the X1, I've come back to it and the mid bass has started to give me some serious ear fatigue. Again, this has nothing to do with the X1 having too much bass. This has more to do with specific bass frequencies and my head/ears not matching up. As I have already mentioned as well, this is a common occurence for me, which has happened with the Q701, 990 Pro, UR40, DT770/600, and some other headphones. The X1 was always tip toeing that line, and being away from it those weeks really put it over the edge.
2. I've listened to music less and less, and played games more and more. The MA900 does what I want (especially comfort and weight), even if it's not completely on the same level as other headphones before it. So for NOW, I don't have any plans on buying another headphone and sticking to the MA900.
As for the MA900, there is no real justification in selling the MA900 when it's not expensive and won't fetch a lot of money, and I can easily use it as a transportable headphone even if I were to get something else in the future. Like I said, it will remain a staple in the same way the Koss KSC75/35 have.
I don't know or care if you're taking the piss at me selling the X1, as it's not like I got bored of it or found something better. The X1 is still very much the headphone I will always recommend for anyone who wants a bit more bass than a completely balanced approach like the Annies.
If I was listening to music as much as before, I could bear with some of the bass fatigue and keep the X1, but I'm not really one to have too many main headphones at once, and will more often than not reach for the headphone I find most comfortable.