Yes I had a #8 and a CSIB and ended up with the S5.5 and agree with Terry it's the best of the lot, and by a considerable margin, at least in my system. Yet it is the cheapest amp CODA makes. I have it paired with an Audio Hungary Qualiton C200 tube preamp, and there is no musical genre the stack doesn't render faithfully, at least to my ears.
Just now I finished listening to two tracks (via Tidal) that had me spellbound:
-Art Pepper's "Nature Boy"
-Leonard Cohen's "The Night of Santiago"
The tonal verisimilitude of the acoustic instruments was breathtaking. Cohen's voice was so eerily "present" in the room, when I turned the lights back on I had to chuckle at my goosebumps.
The system is as follows:
Puritan PSM156 conditioner -> Melco S100 ethernet switch (fiber optic output) -> Lumin U1-> Gustard R26 w/external masterclock -> Qualiton C200 -> S5.5 -> Mofi Sourcepoint 10s (cabling is all by Transparent)
I sometimes prefer this setup to my main setup in the living room, where the amp is a Gryphon Diablo 300 running B&W 804 D4s, especially for small scale acoustical music.
Regardless, the point is IMO someone could build a killer system with the S5.5 at its heart for under $20K.