You answered your own question. I haven't used a mobo soundcard in a long time. They suck for my purpose and depending of your mean of "super-expensive" even my cheapest gear (which has been long gone) was better than any of my mothetboards, with a few very bad, regretful, exceptions.
Then, I have a question, and this is quite a bit of a tangeant, but, I've often wondered why no-one has yet build a modular, upgradeable, PCIe-card-centered Linux-based HiFi receiver. All the ports & interfaces could be on removable cards so upgradeable when standards change; OS upgradeable to support any new codecs & formats etc; get your socket right & CPU also upgradeable although would barely be needed in most cases.
DAC ain't changing much once you have a quality one so it could take up the corner of a standard ATX case; min-itx board would fit the bill nicely and could even be the basis of a full home-AV-centered VR behemoth machine
Unlikely to fir the SFF billing, of course, but I did say it was a tangent