Better cd SQ

Thats a Cirrus Logic chip in that 6006 and I would venture to guess a decent implementation, hence your current satisfaction statement with it.  Proly gonna need to spend more on the DAC than you actually would CD player. 

You can get your CDs to sound as good as your vinyl and streaming can sound even better. The DAC would be the first step. It is a question of your transport and DAC, matched to the rest of your system.

I always look at the long term first. Do you want to improve your whole system over time? In that case each new purchase should be one level up. So, let’s say you do your DAC… then next your transport… or better yet a streamer. No reason to waste money to play the CDs you have when you can have access to millions of albums at the same or better sound quality.

But first things first what is the rest of your system. There is a place under your userID to put photos and ID your equipment. This would be really helpful for us to help you.

I think it’s a very good idea! You can greatly improve the sound of your CDs from what the Marantz has to offer.
You didn’t specify your budget though which makes recommending anything nearly impossible.

A fine idea. Start with a better DAC and graduate to a transport.