I saw a set-up somewhere(maybe here) where a guy made a diffuser out of PVC pipe filled with Bio-Balls and placed it on the outtake of his canister filter. It was placed so the water would push down at about a 45 degree angle and then up to the tank.
He stated it was very quiet and he got 100% mixture of the CO2 into the tank water.
I wonder if that's the one I made your talking about there. I've since made a new reactor that screws apart so I can clean it out if need be. I also cut down on the number of bio-balls from 10 to just 5. I still get 100% CO2 dissolve so I'm questioning if the bio-balls even do much, considering that the CO2 mix is carried about 4 feet before going into the tank.