The XPS should come with a Burndy cable for connection to the CDX. However, if we ignore the earlier inferior grey ones, then there are essentially two to look out for; the original black XPS Burndy or the improved S-XPS Burndy. The latter can easily be identified as it has S-XPS typed on the direction collar. Just be sure you are getting a genuine Naim Burndy cable as non-Naim types are not at all recommended and may, at best, give operational issues, and at worst may cause damage to the connected equipment.