I've just purchased a new dual 1 GHz G4 and plan to run Final Cut Pro on it. I'm looking for the best way to get surround sound audio out of the computer and into my home theater receiver (preferably optically) for monitoring purposes. I will also need to get analog audio into the computer. Has anyone done any research on this ... does an animal of this type even exist?

I'm just researching that very topic for my home business.

Check out the forum at the musicplayer net.
http://www.musicplayer.com/cgi-bin/ultimatebb.cgi

And ther are several related forums at the Digital Media Net.
http://www.wwug.com/forums/index.htm

As far as I know there are no prosumer cards that decode surround sound.

With an app like Digital Performer and an audio interface with at least six outputs.

You can prepare tracks for encoding with DVD Studio Pro.

My Sony home theater system has inputs which bypass the Dolby encoding, allowing you to mix in simulated surround.

There are some pricey devices that you plug your digital outs into that do bass management in real time.

I don't know when it will happen, but with the advent of Firewire home theater speaker systems that do bass management with software. firewire nearfeild monitors can't be far away.

Audiophile 2496 does have OSX drivers and it says it can output to 5.1 but I haven't done it.

The deal is you send it out thru the digital spdif coax but say its not a sound file. I think if I remember correctly. I have not tried it.