Does an external video card output sound via HDMI w/ no integrated sound card?

So I am looking at using a SuperMicro A1SRi-2758F with a Nvidia GT710 Video card plugged in so I get an HDMI output. I'm a little unclear how Audio out via HDMI works. Is processing done on the video card or is that strictly passthrough? If it is strictly passthrough can I use a USB soundcard so that I can get sound out via HDMI?

HDMI on a modern video card is strictly a software sound card with a purely digital output. All processing of the sound is done by the cpu. There is no pass-through of any other audio hardware in the system.

Modern GPUs have built in audio controllers.
ftp://download.nvidia.com/XFree86/gpu-hdmi-audio-document/gpu-hdmi-audio.html