LOL

My DJ/Production/Listening room as it stands today.      

I really have no idea what you mean by "a lot of lag."  The ONLY lag I have with the X5 is the play screen switching the name and album art from track to track if I skip a track.  The rest of the UI is quite snappy and I've experienced no lag with the audio when switching tracks.

  The UI is not as snappy as the iPod Touch or iPhone but it's also operating with much less processing power.  It's about as snappy as I recall the iPod Classic being.  I would call it "acceptable" but not "industry leading."  It's not a deal killer in my opinion.   With regard to the...

No, there is not a BIG difference.  That said, there is a noticeable difference.  The X5ii is more resolving and has a slightly broader soundstage.  The differences are more nuanced than they are "night and day."   I've owned a few around 15 Apple iDevices (various iPods, iPhones and iPads)...

  Oh my God, I had an iPAQ.  I remember that WinAmp-esq motif very well.

  Money well spent.  I've owned some semi-expensive portable gear in my time and FiiO is nothing to scoff at lately.  I prefer my X5ii over my Hifi-M8 because of the size.  The M8 sounds better but marginally and it's a PITA to walk around with.

  Great choice in music.

  They're Sennheiser IE 800s.

I'm disappointed that the screen is plastic and not glass.  For a device that costs more than $500 this is a misstep for Sony. 

bummer

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Congrats all!

  I hope you're wrong.

  I would be flabbergasted if this device did not work with their PHA amps.  It's just a few scripts of code which would allow any ZX100 owner the ability to cough up a few hundred more $$$ on another device.  It's an easy cross-sell for Sony.