Catalyst will not output on the SDI, as the graphics card handles a lot of what catalyst outputs, and the SDI card cannot handle this. In order to get SDI out, you'll need to convert it using some sort of external box to HD-SDI and then run that into the HD-SDI card on the other computer. Make sure you test all of this out thouroughly before you get into a show situation so you can find any kinks before its too late.