YES ! keep the Marantz as a transport and get a Solid state or Tube DAC! There are so many out there,I would recommend you look at something from Parasound,Musical fidelity,cambridge audio,Nuforce..I use a crappy jvc mini system to send a optical signal to a Monarch Audio DIP then out using XLR cable to a MSB Technologies Nelson DAC...the sound is simply awesome.
Matt M
Matt M