Help, Manley Mahi, Oppo-BDP93

I'm using my Manley Mahi mono-blocks with an Oppo-BDP93, using the volume control via the Oppo. My speakers are either Zu Druid Mk04.8 or Dunlavy SC1 depending upon the need, per evening, or artist/recording. My question is; what DAC will better the internal DAC within the Oppo, and/or is my source the issue? I'm using the Oppo with WAV files via an external drive and still listening to CDs and Super Audio CDs.