My Lumin X1 is an excellent sounding streamer DAC. I also appreciate the fine support Lumin offers in software updates and features, such as the LEEDH processing optional engagement, which is excellent and very convenient is one wishes to go direct to amp rather than use a preamp. Peter Lie of Lumin very actively participates on a number of forums and is an excellent resource for quick response on Lumin questions/issues as well as offering pertinent general audio advice.
Regarding Tambaqui, I have not had the opportunity to listen to one, but from numerous reviews and postings, is considered an excellent piece as well. I, too, had been interested in how these compare, and I have only found a reference of both in a 6 Moons review,
https://6moons.com/audioreview_articles/lumin8/5/