I prefer the major brands as they are easier to get parts for in the LONG run. I would definetly get a ECM motor also known as variable speed ECM motor. The Lennox G61V is a very good tried tested and true furnace. May be replaced by a new model in 6 months but they are still available. VERY few problems with them as they have been around for 8 years and all the wrinkles ironed out. The Lennox SLP is also very good with an ECM motor and 3 stages/variable capacity mode. Lennox, Carrier / Bryant are my favorites but finding a long term reputable installer is very important. Nothing wrong with the other brands but there has been a LOT of takeovers of one brand by another etc and in the long run it is hard to get parts for some of them when they have been resold 3X. Lennox and Carrier are so huge that will never happen. The more expensive brands have more extra adjustment features on their circuit boards for fan adjustments etc than the lesser priced brands. You get what you pay for.
Going to be 30-33 deg C for all of next week so I should be busy. I hate high humidity and if it never went over 25 C I would be happy.