Power amp or head amp?
And what transducers will you be using it with?
Monoprice Liquid Spark is worth shortlisting.
Probably an Objective2 with the low gain set to 1x then. It's dead black even with my 119dB/mW SE530s and output impedance is less then 1 ohm.
Can't really thing of anything as good for IEMs anywhere close for the price.
My issue with the O2 is that even with 1x gain and the D10 it is almost too loud on my Shure 535s. On hot recordings I am just able to get the volume knob loud enough to get past where the channel imbalance is noticeable.
That's more of a problem with tiny pots in general. Mine's that way too, but I've never heard anything better at that size. Something with a full size Alps unit or a volume control IC would be be an improvement but more money as well.
Have you had better luck with tracking on something else?
I use the IFI iEMatch if I want to get around the imbalance.