Getting a DAC would certainly help out the sony. Look at either Sonic Frontiers' SFD-2 (tube)or Classe DAC-1 (SS). Can get eitherh for around $800.
OR
Try a one box to replace your Sony. Try SFCD-1, BAT VKD-5, or Meridian 508.20. Though, these will cost more than the DACs.
OR
Try a one box to replace your Sony. Try SFCD-1, BAT VKD-5, or Meridian 508.20. Though, these will cost more than the DACs.