Second System: Add DAC to Marantz CD Changer?

I'm sitting here musing my audio options for my second system, which consists of a Classe 101 integrated amp, a Marantz CC4000SE 5-disk changer, and Linn Tukan speakers. I just recently purchased the kit components to make some VanHaus power cords, and will swap out the cord on the Classe and maybe open up the Marantz and replace its cord.

Wondering what else can I do to make a significant improvement in the sound? This is a CD based system, and will not have analog. Say I'm willing to invest b/t $500-$750 in it. Would it make sense to purchase a DAC for this CD changer? Would it offer substantial improvements - a smoother midrange and upper end? If so, what DAC would fall into this price range (with cable)?

Thanks for any ideas. Just musing here.