Multi-room wireless speakers from HTPC- whats the best approach?

Hi,

I would like to set up a Multiroom wireless speaker set up for my Home Theater setup.

Here is my stack:

• HTPC connected via HDMI to
• Pioneer VSX -921k with 5.1 wired surround speakers.

A limitation of the Reciever is that digital input cannot be sent to anthing other than the room 1 speakers.

Is Sonos or one of the other wireless systems an option? If so- how do I get around the no-digital out problem.

Any help is appreciated- thanks.