Best answer by MikeV
Yes, you can. The Sonos Connect has three different types of audio output: Optical, Coaxial, and analog (red/white RCA). It appears that the RHT-G900 has all three types of connectors, so you should be able to use any of them without issue.
The only concern is that you might not be able to use whatever input you choose for Sonos with an HDMI cable, giving you one less video source. You'll most likely need to use one of the digital connections, since the analog connection on the stand is reserved for the TV, whether it's connected through HDMI or not.