Airmega 450

Honestly, I'm not sure if you'll really notice a difference in terms of performance and getting your air clean. My understanding is that the difference comes from potential longevity of the filters. Having a dedicated removable pre-filter and regular cleaning will prolong the life of the HEPA filter

I assume the 500 sq. ft. you mentioned in another comment is an open space without walls. (You need a purifier for each room, as they can't overcome walls and doors.) If the 500 sq. ft. is open, you would need a minimum of 334 CFM CADRs. These figures are for normal pollution levels. You may have el

Regarding air purifiers, this has to come out, so Coway Korea must be responsible for it. I have had 3 Coway Airmega 450 now, all 3 are defective from the factory, the sensor is broken, the pm meter freezes at pm1, the motor is broken on all 3, no air comes out of the air purifier at all , it cleans