oh thanks! I think I understand.

Can I use optical cable thru ADAT if I have a reverb that has this feature? How will I connect this?
The profire unit connects via firewire to the computer. The ADAT ports on the back allow you to connect ADAT devices, which the Profire also sends to the computer, which increases your channel count.
For example, my brother bought a Profire 2626 and I gave him a blackface ADAT to use with it. So he has the 8 channels of the Profire, plus the 8 channels of the ADAT (lightpiped into the back panel) all firewired into the computer. You can add 16 channels via lightpipe plus the onboard 8 channels of the Profire, giving you a theoretical 24 channels, but I think
the Profire software mixer will only let you monitor 16 channels.
However, you can't set up aux sends with the M-Audio mixer ap, like you would be able to do with
Reaper or whatever your DAW is. It is useful for headphone mixes while tracking though. As opposed to adding effects during mixdown in your DAW, which I understood your original question to be about.
Although your reverb unit may have an optical port, I seriously doubt it uses the ADAT protocol. But who knows, try it and see.
Am I on the right track with what you are trying to do?