In this case, the chip is a VIA 1708S (on an Asus M4A785T-M). It installs Windows 8 drivers by default that work in Stereo for the front speakers. However I could not push sound to all 4 speakers until I installed the VIA HD VDeck and Windows 7 audio codec, and enabled Speaker Fill. Things seem to work great after a restart, but when the computer resumes from sleep, the left speaker crackles but otherwise does not produce sound. The other 3 speakers are still getting sound.
I've attempted swapping out speakers and double checking the wire connection, but it's definitely a driver issue that occurs any time the computer has resumed from sleep. Restarting fixes the issue.