Maybe a pairing issue? Some IEMs are quite picky about their sources... And the clear as day X3i (for it's price bracket anyway) can and will show clearly imperfections in sound (where percieved or not, everyone hears diffrently, true?) coming from the source...

In other words, maybe the analytical (quoting ClieOS here) sounding X3i is just making the flat (so says the people in Head-Fi) sounding, un-EQed Tubie sound crap flatter then it already is...

Maybe... And until some crazy Audiophile shoves a good (yet easy to drive, some GREAT IEMs are near darned useless on mobiles unamped) Higher Class IEM into the 5800 for some serious auditioning (Westones? UEs? IE8s - or are the IE8s hard to drive?), we'll never really know...

EVEN THEN, again SQ is highly subjective... What is honey to one guy can be tar to another... BUT, everybody deserves to share their opinions BECAUSE of that...

I'm still waiting for my "fun" sounding Bijous to come over... Hopefully it would not sound like crap with the 5800 (after some serious burning-in of course, I've heard that it needs what, 300 hours?) to my SE Megabass (muddy as it may be) trained ears...

Totally agree with you.
Best earphones doesn't always produce best results on certain devices.
Pairing plays a very important role too.