Truthfully, you will only know when you listen for yourself in your own home with your own system.
Once you realize the importance of the external DAC you will likely be switching them out like speakers for the first year of two. And they are much easier to switch out than speakers.
Start cheap, Like in the less than $200 range to see what everyone is talking about.
Having said that. The real center of the universe of quality without diminishing returns of money vs quality of sound hovers around the $1000 mark. I have owned and can highly recommend the RME ADI2, the Denfrips AriesII. My own favorite in that money range group is the Schiit Gungnir, frigging love that DAC. All three are different from each other and wonderful with no negatives.
Now I am running the Schiit Yggdrasil OG. Purchased for $2100 used. For me my endgame DAC.
Final note. They all do sound different. And super great measurements don’t count for much in the equation. I purchased a super perfect measuring DAC reviewed by Amir (who I trust), that measured great, sounded like mud.
You have to hear these yourself.