Haven't heard the CD5x but I own the Naim CD5 and the CDX2 and the Linn unidisk SC. I have also done a good bit of experimenting with hard disk servers connected to DACs (mine is the musical fidelity trivista). There are a few things which experimenting with multiple combinations of the above have become clear to me. I always preferred the way the music sounded coming from a Naim CD player over a Linn. The CD5 was even preferred over my Unidisk SC so when I upgraded source I chose the CDX2 rather than a "better" unidisk like the 2.1. The convenience of the hard disk server cannot be beat however if your system has pretty decent components/cables etc. you will most likely readily discern how superior the music sounds coming from an excellent CD player (I still don't understand exactly why this is but I have proven it to myself over and over). I have experimented with everything from the recorded bit rate (wav, lossless, whatever uncompressed form you like), to different sound cards, to external dacs, to most recently using the wireless apple airtunes optical -> DAC. The CDX2 always smokes it. But it is getting much better the more I experiment with it. Remeber, these issues are all relative, I don't mean to imply that any of the combinations or pieces of equipment sounded BAD they all sound quite good (except maybe a basic sound card directly into line level preamp) and it is just a matter of degree of refinement. Good Luck.