I've been wanting to pick up a humidifier (living in the desert does hell on the hair!) as well as an air purifier (having a cat). I know nearly nothing about the technology, and I don't know if a cheapie $30 walmart thing will be just as (or nearly) as good as some $100 unit.

I'd prefer spending as little as possible while still getting a quality unit. I don't have a big apartment (2br) so I don't need some crazy huge thing. Even enough for my room alone or a couple others is fine.