To be honest I hadn't heard of it until now. I still haven't been convinced that going balanced is worth it with IEMs, but it's certainly interesting if it improves the RE-400. I do use my RE-600 balanced with the HM-901 every once in a while - it's an excellent combination.
I just found out about it the other day, but it's apparently already for sale (the bundle goes for $250) - I share the same sentiment about balanced output but I just like the fact that it's amp is purpose built for the RE-400 essentially (and to a lesser extend the RE-600), that being my overall favorite IEM to date. If it does in fact improve upon them, it may very well end up in my collection haha. It was also confirmed that it is capable of being Rockbox'd, assuming they have the desire to do so with this model.