I have almost the same problem as you. Pioneer VSX 1021-K and a new Geforce 660. I have a 5.1 setup, not 7.1, but the VSX 1021-K is using those last two channels for a B zone.
When windows has the VSX-1021 configured as 5.1, I only get PCM on the receiver. And unfortunately getting PCM disables any of the upconversions like neo and neural. I noticed this watching Hulu, in that I only had stereo sound and can't choose anything but PCM.
If I lie and configure the playback device as stereo, then I can set any filter I want.
Rather than change windows settings every time, I rely on the Signal Sel button on the VSX 1021 K remote. I use an optical out from the mobo. When I play something that I know is multichannel, I set windows to use HDMI audio, and PCM performs fine. When I play something that is stereo that I want to upconvert, I set windows to use the digital output (the optical cable). I can tell the receiver what cable to look for audio on because the HDMI input is one of the ones that lets you specify analog and digital inputs as alternates.
Pain in the ASS!
Couldn't get Reclock to work as I guess it's for certain applications. I was just watching hulu in a webbrowser. I have no clue how to tell windows to stop outputting 5 channel audio (2 with sound 3 with silence) on my command.