You really are going to have to keep your gain on a tight leash - you need to make sure your getting as much output as possible from the sources going into the desk as possible.
If you own the desk it's a good idea to check into having it modded; getting it rechipped and recapped reduces the operating noise radically. Creation Audio Labs does a fantastic job with the modification and it can be done incrementally - just one or two channels at a time (or as many as you want) making it very easy to afford.
I own one and keep my input levels to the board hovering around 0 on the meter. I think it really does sound the best at 0, and the noise has never been an issue. Do you have the crappier power supply, maybe that's causing you issues?