I just signed up for PetPlan and am paying about $121 a year for my 2 yo male (neutered), microchipped cat. There's was the cheapest of everyone I looked into. You may already be aware but I was surprised to find out that routine visits aren't covered. The insurance is really more for emergency situations that can be costly. Not for yearly exams, monthly heartworm preventatives, and such.
My cat just had surgery. He was not insured at the time, so we got quite a large bill. I did some research about getting him insurance, but unfortunately, the crystals which caused his blockage are considered a "pre-existing condition." If we were to get insurance any crystal-related problem wouldn't be covered for two years. And if he were to stay on a special diet for crystals for the rest of his life, crystal-related problems would never be covered. Oh well. Good luck with finding a good plan!