Are you getting it for general purposes or to control the bird (and food) dust?
We have not had a lot of luck w/air filters and have spent from $50 to $500 for them. A HEPA filter is supposed to be the best. I think part of our problem with them is two-fold; they didn't seem to do anything and I got worn out with their constant humming!
I hop that you can find something that works well, especially with the birds. (I'm gonna assume that if it works with the birds it will work with dogs and cats, too.)
Keep us up-to-date on your air filter solution. It will be interesting to find if you really get hold of one that works well. Could there really be a way to have LESS dust in the house?
What kind of birds own you?