Get a used or new MHDT Atlantis R2R dac, or Pagoda if in price range. Get adapters to use 6dj8 family tubes in the 5670 sockets, and get a nice 6922, ecc88, 7308, 6n23P, CCa tube for the output buffer. Your CDP will sound more amazing than you ever imagined. Buy a really good s/pdif cable, Enjoy.
Phil