CD Player for Cary system, pls...

Hello Audio Experts! I have a Cary Cinema 6 pre, AVA Ultra 350 amp, & Marantz CC4001 cd changer system. I want better cd sound. Could I have suggestions for a better single cd player, or a DAC for use with my Marantz? Which way should I go; how much will it cost to better my sound, and which units would you all recommend, please?

TIA! Murf