Sure it makes sense but…
\There are only a handful of chips onboard PC mainboards and just one or two dominate the market to such a point that it leaves hardly no room for variation.
Most mainboards have a Realtek chip of only a few varieties. I can safely assume that nearly all of these are equal enough by design to yield the same results in regards to digital output.
So the question can easily be answered.
Is an onboard digital output ‘good enough’ for an offboard DAC? Is jitter so high that the loss of detail and focus for sound staging is significantly degraded? Is this an inherent issue?
Is using a high quality PCI digital IO card enough to make a significant difference?
Is the digital output from a USB device enough to make a significant improvement?
These are the only two viable solutions to an onboard digital output!
I tried (and still own) an M-Audio Delta DIO which is a $300+ PCI digital IO card. Compared to an onboard Intel sound device (not particularly popular on mainboards today) that uses toslink didn’t show a significant loss in detail or soundstage compared to the much better M-Audio PCI card when I compared them some time ago.
Is this why a small handful of companies made special devices that convert USB to SPDIF? RWA puts great efforts in modifying the SB3 just for digital output.
This is actually an important topic since the popularity of PC audio is growing at an exponential rate.