Where can I buy DIRECTLY a new 4-ton gas furnace unit (just the unit - not installation)for the home (80,000 BTU or more)? I am in the L.A. area. Can I buy directly from a gas furnace manufacturer so I can cut the middle man (dealer)? Or, is there any other discount retail source? What I am trying to do is buy the unit myself, then get a local company to do the install - that way I expect to save a lot. Please help. Thanks.