I like my humidifier in the winter when it is dry and Aprilaire is supposed to be one of the best.
I've been checking on air cleaners and Honeywell seems to be the most highly recommended by the HVAC people I talk to. Some will say that they snap, crackle, and pop which annoys some people. I have been researching whole house HEPA filters which install at your furnace/ac and would be inclined to do that although most HVAC people I know haven't heard of them. They get more of the finer particles. Grainger carries them. Places that need clean air such as computer plants and pharamaceutical plants use them rated up to 20 air exchanges per hour.