Go to Home Depot and buy a Honeywell True Hepa for $158:
http://www.homedepot.com/webapp/wcs/stores/servlet/ProductDisplay?storeId=10051&productId=202184299&l angId=-1&catalogId=10053&ci_sku=202184299&ci_kw={keyword} &cm_mmc=shopping-_-googleads-_-pla-_-202184299&ci_gpa=pla&locStoreNum=466
The ones stocked in store are usually white. I used this when I lived in a really old house and it works wonders. True Hepa is recommended by all of the allergy associations. Other air cleaners usually rely on ozone something or other that is controversial and causes some people to have headaches.