Central Station DA for processing and Monitoring?

[apadua]

I would like to take the tracks already recorded tracks and send them out to a compressor then back in to Cubase.

I want use the central station's DA for both monitoring and processing but I am convinced that is impossible b/c I keep getting feedback issues. Here is how the signal is flowing through..

Processing
Recorded track routed to MOTU tos link out in Cubase --> CS (tos link in)--> CS Cue output (TRS)--> Compressor (TRS)--> Lucid AD9624 (tos link out)--> Motu (tos link in) --> Cubase

Monitoring
Main Buss in Cubase (routed to tos link out) --> Monitors (HS80m's)

Results in FEEDBACK...I believe the loop is occurring in the tos link out from the 828…

My Solution

Processing (same as above)
Recorded track (motu tos link out)--> CS (tos link in)--> CS Cue output (TRS)--> Compressor (TRS)--> Lucid AD9624 (tos link out)--> Motu (tos link in) --> Cubase

Monitoring
Created a group channel and set the output to the MOTU main outs (instead of the tos link)
Connected the MOTU main outs via TRS cables to the CS's TRS1 input
Selected the TRS1 on the "Main" input on the CS (monitoring)
Selected the Digital on the "Cue" input on the CS (processing, adjust the output knob accordingly)

Results = No feedback but I am using the Motu's D/A for monitoring. I have been spoiled with the lucid's DA it is noticeably better than the 828mkii conversion.

Is there away use the CS for both monitoring or processing or do I need to introduce another DA device (Lucid DA 9624 for ex) to pull this off.
Thanks,