What is it that you don't like with CD31? It uses Burr-Brown PCM1704-K R2R D/A converters, very good indeed. Newer CD players use Delta Sigma DAC.
Since CD31 has AES digital output for connection to an external DAC, maybe you want to consider getting the recent discrete R2R ladder DACs, including those from China (Denafrips, Holo Spring, LKS).
Since CD31 has AES digital output for connection to an external DAC, maybe you want to consider getting the recent discrete R2R ladder DACs, including those from China (Denafrips, Holo Spring, LKS).