I have tried the Pico, Predator, and iQube all with the UE11's and prefer myself the iQube. I gravitate towards the iQube's control over the lower marks in the FR and more transparent sound signature.
To my ears, the bass on the UE needs no oomph or extra "punch", which the Predator provides to the UE11's. I think the Predator's ability to bring out the high's in certain phones is a strength for many but not needed with the UE11's. This said, UE's highs and MR marks are thrown off or accented in terms of the balance and presentation using the Predator.
I really liked the Pico the best for its looks and compact size VS Pred/iQube. Where my opinions will be applied is per the Amp section of the Pico VS others. I think that amp section alone that the Pico's reproduction of vocals and overall tonal range is bested by the iQube. The Pico's amp section is very good but the Predator's presentation makes for a more involving session, and is slightly better to my ears. This said, the emotional effect that the Predator encompasses is not great for all genres and tends to smear many types of music into the same sound. I think that the Pico's treble sounds a bit artificial or tinny VS the Lisa (not considered portable) and/or the iQube. Realism is a big factor for my music preferences, and in this respect, the Pico is defeated by the iQube due to the increased transparency. I do enjoy the more expanded stereo image of the Pico VS the Predator, although the latitude of the iQube is every bit as spacious or perhaps large. I do not use the DAC section enough to worry about AB'g VS the iQube, however, utilizing the DAC of the Pico really is awesome for the price..and with the UE11 (DAC route hardly portable) Source will vary.
It is also worthy of noting that of the three mentioned amps above that the iQube provides perhaps the largest space back to front imaging, which compliments the UE11's 3d sound signature. Since the UE11 has the largest out head signature VS every other IEM I have tried, the enhanced depth of sound staging is a bonus not overlooked in my transportable world. This helps especially with Classical, Jazz, Soundtracks, and Binaural recordings..among others.
I think too that the UE11 sounds superb straight out of the 2G Touch HP out for casual listening of 320KB and Lossless, FWIW.