So the first post in that link, setting out the premise, is from 2006. I remember back then, using the onboard sound would drop my frames per second as reported, because I was really pushing the CPU or otherwise CPU limited.
But over half a decade later, present day computers, do they still suffer from using the CPU to process sound? I'd guess that you have CPU cycles to spare for use in sound processing, maybe even you have extra cores sitting around doing nothing that could do sound processing (not sure about Starcraft specifics, but I'd guess they use one core for user interface stuff and maybe sound, while the other core does game engine etc., and remaining cores beyond 2 just do nothing).
Anyway, is it still a valid argument that a sound card will let you get higher frames per second because it takes a burden off the CPU?
And more interestingly, will using the videocard's sound card take the burden off your CPU, or does the video card sound via HDMI burden the CPU just as much? You don't really see anyone reviewing this anymore, it's just off the radar as far as trying to increase game performance.
Also, I'm not sure I'm convinced that there really is a burden to pipe the digital sound directly from the game through the video card sound to a digital HDMI sound processing device - don't most games work that way, where they just output a digital sound and, so long as you aren't adding reverb/echo/EAX effects, the sound card just funnels that data through the HDMI port on the video card without touching/processing it?