I was intrigued by Coda too at one point but found it really really odd that the only reviews are in stereotimes by the same author who gushes over them in every article. Not one review to be found in Sterophile, Absolute Sound or any of the other larger review mags.
@speedthrills, I agree there are not many recent Coda reviews but there are lots of older reviews including Stereophile.
e.g.
https://www.stereophile.com/content/coda-technologies-s5-power-amplifier
https://www.enjoythemusic.com/superioraudio/equipment/1104/codas12.htm
https://www.dagogo.com/coda-technologies-cs-amplifier-review/
http://everythingaudionetwork.blogspot.com/2016/08/ean-audiophile-review-coda-technologies.html
I believe they have been making amplifiers from ~1989, so I don't consider them a niche brand. The many positive reviews from members here and other sites like WhatsBestForum regarding Coda led me to purchase a S5.5 after owning two Pass amps, and the reviews and strengths were spot on to my ears. I'm very happy with it and don't miss either Pass amp (specially the summer time heat :)), not that they both were not great amps too and gave me years of pleasure.
Regarding the posts regarding resale concern, if you use HiFi Shark folks can see many Coda amps selling over many years at reasonable used prices. ~$4K used for the $6400 S5.5 (upgraded model) or ~$3500 used for the $6100 XA25 isn't a big difference either way.