Fostex and a few other companies make a "repeater" that will let you connect a few of them together. I forgot the model number, but it is essentially made for that purpose. I put on in my parents' system to convert the digital output on a DVD player from toslink to coax (toslink out to Fostex box input, coax output on Fostex box to 5.1 preamp). It works just fine and passes along 5.1 info. Also, it cost around $100. I bought it at Mars Music (big musical instrument chain store) in the studio dept.
Brad Day
Atlanta, GA