Dursos, Stockman, HGB, all have air in the lines, just how they work. For no air, it's a Herbie or Bean.
I switched from dual overflows and Dursos to Herbie (
here) for the gurgling and all I can say should have did it years ago. Noise from the display never was a problem, just the gurgling in the lines and bubbling in the sump. Now there's not even micro bubbles in the sump from the drains.
Can also run a Bean on dual overflow chambers. Huge thread but check the RC thread (
post 2495, page 100) on setting up. Never tried but hype seems a Bean might be better than a Herbie as allows more of a range before needs adjusting.