word request - A more positive term than "obsessed"

Below are four different situations describing people's obsessions

1. 
   

   A friend who loves everything and anything to do with cats. She has five cats at home, and there's more cat food in the house than "human" food.

   
   


2. 
   
   

   Another girl friend has a weakness for white-haired men, she finds them irresistible, they don't have to be old-looking, but they must have a mop of white hair or as the Italians say, "salt and pepper hair", but with more salt than pepper.

   
   


3. 
   

   A male friend only dates women who are petite, and extremely slim; not anorexic but women whose dress sizes are 38 in Italy. I think in the UK that would be equivalent to a size 8.

   
   


4. 
   

   Another male friend who is mad about skiing, will happily drive for two or three hours until he reaches those snow-capped mountains, and ski uninterrupted from 10.00 in the morning until 04.00pm (when dusk falls).

   
   

Now, I could say that they are all obsessed, but that term, more often than not, carries a negative connotation and I don't want to express disapproval.

I could say love but that word is overused, and I want something a little more original.

• Is there a positive word and/or unusual expression that fits all four scenarios?

It can be slang, American, British, or Australian English, I don't mind. The more original and good-humoured, the better.