[tech_head]

Not sure of your configuration.
Why not have 3&4 analog go to the C24.

Then you have multiple master faders control the analog/digital.
Assign the same bus to input both master faders.

The C24 has multiple inputs and use it to switch.
The problem there is that you will be hearing the C24 analog and not the quality of the D/A in either your outboard box or the 96 I/O.

The only real way to do that is to have a passive switch box connected directly to the input of your monitor amp and A/B the converters.

Hope this helps.

Tech