SOME onboard sound, certainly not all and usually more recently, use ESS DACs and pretty good opamps. The headphone out, often thru the front panel out in a full-size PC, is where you'll find the special sauce. Jimster, I'm well aware of the technical details of what you're saying and why, but every once in a while onboard is pretty good, and maybe even better than, say, an older cheap Schiit. You'll usually find this on higher-end motherboards, for sure, like ROG Crosshair and Maximus etc, but it exists, so let's not rule it out as a 100% generalization.
Now, with that said, my Fosi SK02 is sitting right beside an ROG Crosshair VIII that has ESS ES9023P. There's not much audible difference, and I won't go much into specifics here unless asked, but for $80 the desktop convenience of the SK02 is very nice. 1, I like to swap out PC parts frequently. This mobo may not be here next year. 2, due to nibbling pets, I can't leave my headphones out, so frequent plugging is even easier than PC front panel. 3, big ol volume control right there, and it's multi-function as well. 4, I'm using a short Type C-C USB4 cable to connect the Fosi, but a Type A-C USB2 would be fine, as would optical although you'd still have to power it via its USB connector. So, it's versatile.
Now the quick and dirty subjective, although it's quite discernible to me, so I'd love to get another set of ears on it soon. Device EQ's flat, enhancements off, Windows EQ flat, enhancements explicitly disabled - onboard was punchier down low, and Fosi is punchier in the mids-to-upper, mostly mids. In the end here, the power supply for both is the same - the PC's EVGA P2 Platinum. By punchy, I don't mean sound quality, just audible hump.
