I had the Minibox E+ amp couple years ago and if it's the same as the Minibox Card (I think someone said it was) then it's probably not a good match for low impedance IEMs. The E+ was designed for the er4s in mind (and the er4p w/ the 75ohm adapter).
The balance card would be a better choice even for single-ended IEMs, IMO.
Thanks for that...I will avoid it since I have mostly low impedance.
You don't need balanced cables / headphones to enjoy the better SQ of the Balanced amp.
It's reported to be better sounding (than Std.) even when used single ended.
Also, it has less than 1 Ohm output impedance which will make it work perfect even with low impedance multi BA IEMs.
I know I will not NEED to, but I will be sooooooo tempted to :)