I still don't really understand IEM centric users looking at this unit. It's obviously meant to run cans that need loads of power (ie. 1.5w). It's also not anywhere close to what I'd look for size wise in an IEM based system (though some run CLAS stacks for IEMs, too).
I get that some may want to use IEMs with it sometimes, but I don't think it should really be tailored to IEM users. If they can do an 1/8" jack easily, great! Make it work double, or triple duty...but if it's something that would increase cost, or be difficult to do for Centrance, forget it.
One of these seems like the best thing to me. It's very low profile, and won't degrade sound quality. Won't stick out any more than the volume knob itself.