iMac < > Sonos Playbar

I'm thinking of buying the Sonos Playbar: http://www.sonos.com/shop/products/playbar. Not sure it will link to the 3.5mm optical jack in my 2010 iMac. Sonos tech said the iMac needs to "force the output to always be PCM 2 or Dolby Digital 5.1" Anyone?

Thanks!