Obviously it's in the digital domain. And, there is nothing you can do about the unit "noise" - if you're using that unit, you accept it's offerings.
Dood - I don't have the manual in front of me, but memory serves there is +/-12 dB on each band pass, allowing a 24 dB relative gain differential between band passes. That should be plenty? I sincerely doubt few systems are so far "out of the ball park" that this would not be enough. dbx aren't dummies in this. I was merely pointing out that your comment was limited in it's scope - it did not acknowledge there is ample gain accommodation, by band pass, available on-board.
Bad starting point, and bad idea. If one is embarking into this arena, you are accepting the responsibility of needing a greater understanding of what is going on, and should learn how to work with the acoustic animal you are facing. Get some proper measurement equipment and knowledge - neither is too expensive nor arduous. You can get a LOT more out of this unit by limiting it's auto-functions. That said, I merely know how to run them - I run into them frequently, but own zero of these.