As I am going through my search for new furnace/ac, I have had several reps say the I should get a 4 or 5 inch filter (merv 10) with the high efficiency furnace (Trane/Amana) that they have recommended as the filter will keep the furnace clean and more efficient requiring less repairs and maintenance over the long term. The Rheem guy said I could if I wanted to but a regular 1" filter would be fine- why spend the money. Note I am not talking air quality here but the impact of the filter on the furnace itself. Also consider that I will have it inspected/cleaned every year. Comments?