I don't about unit to unit comparisons. But these manf. are the top three. I chose the Trane for my own home. The Lennox units are very good, but depending where you live parts can be hard to get. I was told by a couple of contractors if your house is over 2,000 sq.ft. to go with the 90plus. Otherwise it will take to long to recoup the extra money. As far as air-cleaning goes, you at least have to have a filter. One step further would be a media type filter. These basically are a pleated filter about 4" wide. I was told that they get more efficient as they become partially clogged with dust. Does'nt make sebse to me. The last would be an electronic air cleaner. This unit is electrically charged and attracts the dust to a charged grid. This is supposed to be the best. I would definately have the ducts cleaned. Make sure when your comparing your prices you are comparing apples to apples. Good luck!