Pico Power > UERM

High gain:

Excellent finish, best ever in a portable amp, better than Slim.  Jeckyl and Hyde signature.  Can have excellent dynamics, forward sound, excellent clarity and full 3D rendering of instruments.  Awesome dimensionality and rendering of frequencies above 500hz.  Can be a bit soft and veiled in the low end.  Performance and signature coherence will be frequency/track dependent. Can be nice and full but also too rich, sounds sometimes overwhelmed w/ certain songs.  Could be overdriving the UERM?  Too much reverb/richness in the low end at times.  Bass sustains a fuller, longer growl than it should.  Smoothest and most refined gain setting for IEMs or anything.  Much more air, separation and space for the music to breathe than lesser gain settings.  During Gloria, you can hear where notes start, extend, linger and die out precisely.

With headphones, not enough power to bring out the low end of the HD800.  Less impact, clarity and texture that you would actually hear using IEMs on the same Pico Power.  Simply not enough juice leaving things less articulated, precise and dynamic compared to the Super7/PWD.  Things start sounding more blended and less punchy, clear or dynamically involving.  Flatter, less resolving.  Sounds decent though for the price, better than a lot of other desktop amps that cost more because the market basically puts out crap.

Medium gain:

Flatter presentation, much less refined. Harpsicord opens up, veil lifts. Less rich sounding, more analytical (too much so). Less natural timbre, micro detail, air and plankton. Less microdynamics.  Vocals and instruments sound mechanical, timbre is just wrong. Similar signature to the PPAS.

Low gain:

Sucks, blurred mess, soft, indistinct.  Pretty shit sounding tbh.  Overly warm.  Get a Fiio. Sounds fractionally better than a SR71B single ended from TRS.  That is not a compliment. Resolution depth and musical body completely crushed.  Going back to high gain is so much better even w/ the quirky, track dependent signature.

Leckerton UHA6S mk2 v. Power (both high gain):

Leckerton has more plankton/low level resolution.  Tom Sawyer reveals more micro dynamic swing, just more agile in complex passages.  However, more forward and less refined, less macro dynamics and macro resolution in areas where the Power shines depending on frequency/track in question.  Pico Power gets some instruments on some songs so damned right, then other instruments sound too soft and indistinct.