Spent a lot of time researching and reading reviews before I decided on the BreathSmart 75i. My 2 main concerns were noise, since it will be in our living area where we watch TV, etc., and would be powerful enough for the space which has very high ceilings. It’s very quiet, can barely hear it running at all, and we have already noticed we are less congested, the dog isn’t scratching anymore, and less dust. Well with the cost.