Sonica will output 5.1 sound (optical) from any computer with a USB port. I'll toss in a 10m optical cable so your mac can be about 35ft from your stereo.
Digital transmission is beautiful, no singal loss. Try going 35ft with an RCA cable.
$50 shipped
oh, I go by toddeddie {remove for sp}@m protection)@ mac.com
Please don't reply here, I may not login often.