...The only slight shortcoming I've read or heard about the Nico is slight dynamic compression or restiction. I'm really curious if the tranquility is better in that area, or if it also gives up a little dynamic pop to the best digital sources. Dynamics are high on my list, as well as tone, weight, detail, air, staging...haha, kind of want it all.
Hey gprro.
I've not had any experience with the Nico but, still, maybe I can help here.
To my ears the Tranquility is, regardless of cost, one of the most dynamic DACs I've heard. Honestly, I've heard equal but I don't believe I've heard better. IMO that's saying a lot for any digital.
I judge dynamics by two criteria: Ability to startle (with large transients) and how deep I can hear into the recording (small, low level transients)
Couple of pieces of music come to mind that I use as a reference to judge this....
Having become familiar with the music and even though I know it's coming, it still startles or surprises me:
Gregorio Paniagua's "La Folia" on the Harmonia Mundi label, track 7 "Nordica et desolata / Aurea mediocritas" @ 3:59. The slap here should absolutely POP! It's subtle but there should be plenty of low end content here too.
"Further Attempts" on the MA Recordings label, track 4 "Before... After". The whole song. This is an acoustic recording and there's things happening between the musicians that are way down in the mix. Some of these things are so subtle that they almost seem like a "suggestion" while other parts of the song set up a sense of anticipation. This is a great example of low level dynamics. Lesser front ends simply miss the nuances that happen here.
Dom Um Romao's "Saudades" on the Water Lilly Acoustics label, track 4 "Lynces B". The whole song. Another acoustic recording with lots of ear candy. Dynamics play a big part in portraying the acoustic venue and the perspective of how everything relates properly. Hard to get right - the Tranquility is exceptional here.
For reference, here's RSAD's System description:
RSAD Reference SystemBottom line I suppose: Within up to around $6000.00, RSAD could use any DAC I want for product development or just enjoying music with in the reference system here. I'm very content with the Tranquility.

So, hope that points in a good direction for you gprro.
Cheers!
Robert
RSAD