Many of my clients are allergic to cats to varying degrees, but it's important to know that allergy to cats does NOT mean you have to give them up. This recent article in HealthDay discusses the problem and how many cat owners cope.
For years I have been recommending that my clients get a copy of the National Allergy Supply catalog, and now I have a link to their website (since paper catalogs are so passe). They have a very helpful air cleaner comparison chart here.