Thanks for all the input. I guess I'll just wait and see how it is. I had a ceramic diffuser that chirped and it drove me mad. Yet piping my CO2 into a powerhead provided an irregular but tolerable sound.
I build my cabinets so they're well enclosed all around. Hopefully that helps. I don't think removing the impellers is a bad idea either. The home made PVC diffusers achieve a nice level of diffusion without using them or bio balls.