Congrats on retirement! Wishing you much listening pleasure from your excellent system.
Heartily agree on your observations of the Tambaqui. All these years after its debut (an eternity by digital standards) I am not sure I would pick anything over it at even twice the price.
Incidentally, which dCS did you audition? I heard the Lina with clock at a dealer and thought it was quite good, but couldn't say how it compared directly to my Tambaqui. Without the clock I am fairly certain it was not as good - it lost a lot of depth and detail. With the clock, likely competitive, but that is a lot more money. You could get a Makua with DAC module (identical to Tambaqui, both electronically and sonically) for less and I am confident that would be easily superior to the Lina without a preamp, and likely even with a $10k preamp.
What source are you using for the Tambaqui? Not to upset the peaceful bliss of your retirement, but... I finally and very reluctantly upgraded to an "audiophile" network switch (like $900, not something insane) for my Grimm MU1 feeding the Tambaqui, and I admit... it makes a difference. Comparable to, maybe even greater than, adding the external clock to the dCS Lina. I haven't tried it with the Tambaqui's ethernet port yet but I have to imagine it would have a similar effect there.