I would say +1 to the golden retriever. Sounds like it's about what you are looking for although I am not really sure how they do with cats.
For me, it's Border Collies all the way but they are smaller then you want, and contrary to popular belief they don't mind spending a day in the house relaxing, it just can't be a everyday thing. Tons of exercise isn't necessary for them either as long as you keep their minds active. Mine tend to stay active in the house by playing with my two cats. She likes to herd them around. She doesn't hurt the cats at all, and the cats will wonder away from her when they get bored.