I just wanna say this to avoid a lil confusion i saw above.
There's a difference between A/D and D/A converters lol. It's obvious... they're opposites. The OP mentioned D/A converters, so the comments above about A/D converters are correct... but don't apply here. Just wanna avoid confusion.
For my 2 cents... D/A converters matter, only when you're good enough to hear the difference. When I finally got good at mixing... I didn't realize how much my converters were holding me back, until I accidently got better ones by changing interfaces. It was a big difference for me. But it was zero difference to everyone on my team who didn't mix. Yeah... stock D/A conversion on your interface is definitely good enough. You only upgrade that when you've outgrown them and really require hearing minute details in your sound, b/c you're getting THAT surgical with your mixing. Most people eventually get there if they stick with it and decide to do their own mixes. But they come with a hefty price tag... so it's tough to warrant spending that much money.. unless you really need to. Monitors and acoustics will play a bigger role anyway.
Why is D/A different from one interface to another? Think about it in logical terms. A digital signal is literally just a bunch of 0s and 1s. THat sh-t needs to be converted into SOUND. Like.... REAL LIFE SOUND!!! Imagine turning your brain's electrical waves into SOUND. How crazy is that?!?!? THat's essentially what's happening. The digital signal is carrying all of things information (stored as a 0 or a 1) and the converter has to interpret that and produce an audible tone or signal. Certain interfaces needless to say do that better than others, and they come with a price tag. Worth it to a professional. Not worth it to a non-professional or hobbyist.
The prosumer gear is good enough to where you get a good sound. But there is a big difference between that or the high end stuff. It's just a matter of if YOU will notice the difference... which u probably won't until u get good, and have great monitoring and acoustics. For example... a photo is just a photo to most people... but to someone who's deep into film... they se all types of depth within the photo, lightning issues, something may be out of focus... etc. But to me... the picture looks fine enough. Same thing w/ audio.