With the Eitr, you're not using the Mimby's USB input. The USB from your PC goes to the Eitr, and the Eitr reclocks it, regenerates it and outputs it as SPDIF/Coax, which then feeds the Mimby. It's just a way to get Schiit's USB Gen 5 tech for the Mimby and, as I said before, the Mimby's USB input is compromised. Its Coax/SPDIF input is far better.
That's the Wyrd you're thinking of, as it just provides separate, clean USB power for DACs, which the Mimby doesn't need since it generates its own power. The Eitr is a USB to SPDIF converter.
Bottom line is, if you think your system sounds fine without it, then great! You probably don't need it. I bought it because my primary source is my PC and the Mimby's USB input just isn't as good as its TOSLINK/SPDIF inputs and the Eitr's.