In the PCI-324 console, set Bank C to S/PDIF, enable the inputs and set the outputs to "from computer." Select 2408: S/PDIF as your clock source. Set the clock source of your dbx to internal and make sure the sample rates match. Set your mixes output to S/PDIF and create a new stereo track with the S/PDIF input selected as it's source. You should now be able to re-record your mix running out the S/PDIF port, through your dbx, and back in the S/PDIF port to the new stereo track. "Bounce to Disk", of course, will not work with an external real-time loop.
Another option is to send your mix out analog 1-2, which shows up on the S/PDIF out labeled "DAT" as well. Try this if you have a problem with creating a feedback loop with the other routing.

thanks!!!!
I actually just figured it out last night, but your post was right on.
thanks again,

Michael