Someone on the forum already asked before why his Pico was sounding so low in volume. I was starting to wonder about this to so I did a simple test. Set up exactly the same Omnisphere patch in EigenD as an audio unit instrument and in Plogue Bidule. In Bidule, Omnisphere is driven by the midi output of the Pico on the IAC bus. When I play either instances of Omnisphere you can see in the volume meters of the plugin that they both play at the same level, however the sound that comes out of EigenD is easily only half the volume compared to what's coming out of Bidule. I suspect something is wrong in the gain structure somewhere in EigenD.
I recorded a video about this so that you easily check it for yourself:
http://eigenzone.org/EigenD%20Volume%20Problem.mp4
The left side is the EigenD browser with the audio unit 2 being Omnisphere, the right side is Bidule and Omnisphere. I first play external midi (Bidule) and then the internal audio unit, then switch back to external, then back to internal. You can clearly hear the differences.