DA converter hook up?

Hi, dumb question! I have an Acurus ACT3 and with this (2nd) system I use a NAD 545BEE CD player. First off, would I gain from using a DA converter having such an older pre/pro and how do I hook one up? Thank you all for your time and answers.
You would run a digital cable from the NAD to the DA converter and the analog outs from the DAC to your Acurus pre-amp. Not sure you will get a much better result, your cdp is good and the pre-amp is average...