Too Much Maintenance!
I own THREE of these Quadras. These things are more trouble than they are worth!
Although they clean the air (somewhat), they require VERY frequent and VERY thorough cleaning (NOT because my air is any dirtier that yours either).
Cleaning is required almost weekly, never any longer than 2 weeks, and to clean them thoroughly is VERY DIFFICULT. If they are not cleaned regularly, they become very noisy, making highly irritating static and crackling sounds.
To clean them, I remove the grids, take the remaining cases/enclosures outside, and blow them out thoroughly with compressed air. Then I turn them upside down a few times per the instructions, and then I blow them out some more. And then I wash and dry the grid as the instructions call for. What a PAIN!
Also these things do not come back on automatically after a power failure.
I am sorry I bought them, especially considering how expensive they are.