I think an English Shepherd would be a good fit, or, similarly, maybe an Aussie.
A female ES could fall slightly under your size preference (I find most are 45-55 pounds, but it is not uncommon for them to be more or less), but a male would most likely be 60 pounds or more.
Very cold tolerant! Easy care, teflon coat. No need for pro grooming unless you want to have them blown out when they're blowing coat.
Overall a healthy breed. MDR1 is not terribly uncommon, but a good breeder should test parents. It's simple in the way that a dog either has it, or doesn't
I would personally hold out for a breeder that tests hips (either OFA or PennHip) as that is another ailment in the breed. Some working breeders don't test, but a lot do. It also might be worth it to ask your breeder if there's any history of seizures - they should have a good understanding of their dogs' bloodlines and history.
English Shepherds tend to have an AWESOME off switch! Even Quinn, who tends to be a little higher energy than many, has always had a very natural off switch that I've been sure to nurture. Like any breed, bad habits can be formed, but I would say that if you're careful to maintain that off switch, it does tend to be a breed trait.
Most ESs tend to be slightly aloof - at least, a polite disinterest in strangers/preference for their people. I have met a couple friendly ones (Quinn is like this, too), but for the most part I think most of them are fairly "eh" about strangers. Even Quinn, who loves just about anyone, will bark very seriously if anyone tries to come into the house uninvited.
Living with cats also shouldn't be an issue, especially if you'd be getting a puppy.