My thoughts are we either replace the O2 and cat or replace the car. My reasoning is that we already had 1 cat replaced under warranty so I'm betting the cat is going bad if it is not already. My other thought is well how long until the 3rd one dies meaning we are getting it worked on again?
My wife wants to replace just the O2 sensors and see if this fixes the problem. Then if the cat goes she wants to replace the car.