My $0.02: Unless your mixer is mastering studio quality, I'd lose it, fast! My experience with inexpensive mixers, both cheap and broadcast quality, suggested that these are not intended for high quality music reproduction. Besides, having fewer components in the audio chain is usually a good thing.
That said, a DAC may be a nice improvement for your CD players. However, without knowing much about your CD players, I would want to try a DAC out first. For example, the popular Channel Islands DAC and PS Audio DAC are available from authorized sellers and the manufacturers' web sites with a 30 day return option. That way, if you are unhappy with the results, you can return it. Remember to use a quality digital cable between the CD player and DAC. While the DAC will be a big factor in the sound, the transport also plays a role. In most cases, an outboard DAC cannot reduce jitter that the CD transport passes to it. A well designed one-box CD player will reduce jitter, and you don't have to worry about a digital cable.
You should decide what your budget is for either a CDP or DAC, and continue to research here and at other web sites as well. Once you post your budget, you'll probably get plenty of suggestions for DACs and CD players. Auditions may be helpful, but there is nothing like installing a possible purchase in your own system in your own room to determine whether it's a good match for your system.
