External Firewire Port For Mac

I have searched through forum after forum and I guess that means that this is an unsolved problem. I am running a MP on 10.4.8 with the ATI Radeon X1900. I am currently supporting dual-Dell monitors, so both DVI ports are occupied. My goal is to be able to sit in my living room, one room away, with my wireless keyboard and run Front Row on my MP through the TV and stereo system. I have already completed the plist edits to allow Front Row to recognize my wireless mighty mouse as a remote control. I was under the impression that I could take Firewire 400 out of my MP and through my ADVC-100 for a conversion on the way to my television. I realize that Firewire video out is supported through programs like FCP or Motion, and, while I have those, what I need is a mirroring of my main monitor. I did have one success in splitting my audio line out so that one line ran to my computer speakers and the other line went to a 1/8' conversion cable to RCA plugs. This brought the audio to the stereo system. I have looked into the option of the DVI to Video cable for the Mac Pro, but I was wondering if there was a way to simply allow the system to send a mirror of my main monitor continuously through Firewire. haha complicated I know. I would appreciate any assistance
Mac Pro Mac OS X (10.4.8)