I need to replace my gas furnace. It is a 30 year old Furnsman brand. I am not going to ask about sizing or ducts because I will have a heat loss calculation done and I need to do some duct work so I don't over size the unit which I understand is a bad thing. But if it would help, the house is 1050 sq ft with basement 60% in ground built in 1978 (r-12 walls, r30 ceiling, energy star windows). I live in the interior Canada it get down to -30C.
I am on a tight budget(I know so is everyone else). There are so many brands of furnaces out there. Which Is the best built. which is the easyest and cheapest to repair.
I know that everyone has there opinion. But I need to start somewhere and I thought that people that fix furnaces would have better insight.

Thank you