Should I buy a seperate dac?

I had a NAD CD player from around 2010 that cost about $500 at the time. Years later I added a Cambridge dac magic that I bought used for about $300 and it was a more natural sound. My system at the time was JBL speakers , Carver amp, and a Parasound pre. 
In the 90’s I had a Yamaha cd player (1985). When it crapped out I bought another Yamaha (1990). All bottom end players. 
back then, digital was digital right? Well, as soon as I turned it on, I noticed a huge difference. It wasn’t until years later that I learned about better DACs. 

Correction.
That NAD I had was the c 525bee which sold for $350. I still have in in my workshop

Generally speaking, an outboard DAC will improve your sound.   That's always been the case with me, at least.  Of course, there are exceptions.  That's why I said generally. 

Listen for yourself, is my honest suggestion. No reason to spend money on an alleged value that your ears don’t enjoy.

You may find a DAC that for you is just super delicious sounding. That’s when you buy.

In today's day and age though a streamer/DAC combo may be a better value for you, giving you an excellent DAC plus the ability to listen to music from Qobuz or Tidal and hopefully an excellent user experience.

Not sure if you can still find them, but the Parasound ZDac was an absolutely great sounding DAC for peanuts.   If you are dac-curious, a unit like that would not set you back too far.