CD Transport quality

[zdenes]

I have switched from a NAD Silver Line S500 CD Player to a Project CD Box RS with power box RS uni. Both connected via AES to my Expert 250.
Between this switch I had tried Audirvana on a M1 Macbook Air with ripped CDs (Exact Audio Copy) connected via USB.

For me the sound quality with the same CDs was better with the NAD than with Audirvana. And the CD Box is much better than the NAD.
Maybe a DDC would could change this ranking.

Almost any CD player will sound better than a Macbook or a simple PC. You have to compare file-based playback to CDs using purpose-built devices like models from Auralic, Lumin, Innous, SOtM, Grimm Audio, etc, that cost as much as your Project CD Box. Or at least, as you said, use a high-quality DDC with AES/EBU output or Spdif. Otherwise, such a comparison makes no sense.