Simultaneous USB and HDMI Output from Mac Mini?

I've got a Mac Mini hooked up to my HT Processor via HDMI. I recently bought an Arcam rCube and accompanying rWave USB dongle. For those who don't know, the rWave streams audio from the Mac to the rCube using Kleer wireless technology. I was hoping to be able to play music both on the home stereo (via HDMI) and wirelessly through the rCube using the USB rWave. Since the rCube is fully portable, I was hoping to be able to put it in the kitchen or on the patio to extend the music when we are having a party or working the kitchen or just working around the house. However, it appears that I have to choose either USB or HDMI for the audio output on the Mac.

Does anyone know of a way to have the Mac output sound on both the USB and HDMI ports simultaneously?

Thanks.