Transports wear out. DACs do not.This is true, and to many enough reason to go separates.
But from what I’ve learn’t from some digital gurus.
For the best "sound quality" transport to dac coupling, you can’t go better that a single box cdp.
As the one clock inside cdp’s runs both the transport section and the dac section so both are syc’d to the same clock.
In separates each have their own clocks and cannot be syc’d together.
Unless you go mega $ DCS system, which has a separate connecting interconnect between dac and transport so they "both" run off the one clock from dac’s clock.
John Westlake first did this back in the 80’-90’s with his $$$$ Cambridge Reference 1 two box transport and dac, with a separate coax taking the clock signal from dac to back to the transport, but this duo was so expensive to buy, and I don’t think it was too reliable..
May have been 3 box, dac top with volume, cd transopt and power supply for both bottom
https://www.stereophile.com/images/styles/600_wide/public/487camb.promo_.jpg
Cheers George