Got my X3 a couple of days ago. Well, I'm a bit disappointed, and here is why. While it certainly sounds good, I really can't tell it apart from my Cowon D2+, or the CIip+. It has much more power to drive some big cans, but as I don't have those and use mainly use IEMS, I don't really care.
I'm using some nice IEMS, as SM3, DBA-02, RE-252 Sony EX600 and have also tested with Senn HD555.
I made a special switch with two jack plugs and one headphone output, so that I can switch from one DAP to the other without having to pull the headphones out. After normalizing the volume, and playing some high quality FLAC files, I am barely able to tell them apart.
Actually, the Cowon D2+ lacks a little thump on the low end, but the difference is really, really subtle. (that's the famous Cowon bass rolloff probably) The Clip + doesn't display this. Other than that, I really can't tell them apart. I expected a difference in the soundstage, detail reproduction,... but no. Then again, I was wondering how two players that display the same freq response could actually sound different, well, now I know. To my ears, they don't.
Here I'm talking about the Cowon set to flat, all settings off. Once I play with the BBE settings, I can get a much nicer sound.
This actually comes as a surprise. I consider myself a music lover (and I'm a musician), and I have a good hearing, but I'm probably not an audiophile stricto sensu. From what I've read, I expected to be able to hear the differences easily. I am using some nice iems, and I can clearly tell the apart and hear what they've to offer. Not so with the different good DAPs.
My conclusion is that for me, it's not worth the hassle. The X3 interface is not terrible, but the Cowon's and Rockboxed Clip+'s is much better. Battery life is ridiculous compared to my D2+. It is also much bigger and heavier. The Cowon also has a better screen. It is also much faster....
The only reason why I'd consider keeping the X3 is for its powerful amp, if I need to power big cans. But I don't.
Sorry to be a mood killer, but that's my honest opinion. And I think some might actually think alike.