Consumers Reports tested numerous brands a while back and listed the top rated
American Standard, Trane, Rheem.......Rated in the middle werre York, Carrier Lennox.
Standard 80% AFUE furnaces should have a 20 year warranty on the heat exchanger. Hi-Efficiency furnaces should all carry a LIFETIME warranty on heat exchangers. Central Air should have a 10 year warranty on the compressor.