With my RE-400's I slightly prefer 2.1, but with my Audiofly AF-78's I prefer 2.14b by a large margin.
Just have to add that I think the AF-78's are an underrated and unappreciated IEM on Head-Fi especially for the price I paid for them. New the AF-78's list for about double what the RE-400's do but I got them on sale brand new for less than what the RE-400's list for and they are, with my X3 much better sounding IEM's in my opinion, no comparison. I know this fly s in the face of what most would and have said here and I really can't understand this, because to my ears there really is no comparison. Yes the AF-78's are not as comfortable, they don't do deep insertion which I much prefer, and there is really no way to wear them over the ear to reduce their considerable microphonics, I just use the shirt clip, and their carrying tin is laughably small to comfortably fit the IEM's, but the sound once they are fully broken in is so superior to the RE-400's in almost every respect and I don't really think that this is just a matter of preference. I have been an audiophile for a long, long time, but into high quality portable audio for a much shorter period of time and I can say that the Audiofly phones sound much, much more like a hi-end two channel home stereo than the RE-400's. Instruments just have much better tonal quality on the AF-78's, the bass is full with impact but not over done and they render reverb and acoustical spatial information that exists on recordings much more convincingly, and there is just simply a level of refinement in the overall sound of the AF-78's that the RE-400's just don't have. I know that some have mentioned that there is just something not quite right with the mid-range rendering of the top tier Audiofly's and I admit to having heard that before break-in but that characteristic is totally absent now.
In any event enough of my off topic ramblings, but if you have the opportunity to audition a pair of Audiofly AF-78's, fully broken in, you may just be pleasantly surprised. They are a solid bargain even at full list and an absolute steel at the price I paid for them. I have interest in many other IEM's and [size=x-small]I still plan on picking up a pair of the Dunu DN-1000 or 2000 and perhaps a pair of Vsonic GR-07BE's to expand the [/size]collection[size=x-small] and to broaden my spectrum of sound.[/size]
[size=x-small]And just for the record no, I do not have any affiliation with Audiofly or any other electronics company for that matter.[/size]