i have two honeywell air purifiers that I got last year and have worked VERY WELL> they have permanant filters and all it takes is 3 minutes TOPS and a canistaer vac and they are clean for a month! voi la!
yeah the ionizers are awful and I sold them all last year at my yard sale, after thay sat for a year unused. I hear the ones that us a UV light to kill stuff works very well, they are just $$$.
I have a dehumidifier, and the problem I have with it is the water inside makes stuff grow and you can feel the slime even though I don't see any mold or smell it, and I empty it at least once daily. I don't know if that would happen with a purifier though..
if you go on Amazon .com and look up what you are interested in, there are TONS of user reviews to read about that particular product that can help you decide what to get, I like them because they give you a real-life view of what it would be like to actually use the product.