I had three companies quote me on installing a new high efficiency furnace in 2010. Preferred Air wasn't the cheapest and it wasn't the most expensive. They were the only ones however, who actually said they would come in and do a heat loss calculation to determine what size furnace I actually needed. This is extremely important and I would advise people to only go with a company that does this before hand.
After they did the heat loss calculations and due to the fact I had just upgraded siding and attic insulation, PAL recommended a 40,000 BTU furnace rather than the old 60,000 BTU one currently in place.
The other two companies simply asked, 'Well what do you have now?' I said a 60,000 BTU furnace and they said then that's what we will replace it with. This despite the fact the old furnace was 22 years old! Uh, I'm pretty sure the technology has changed and the new furnace is 'High Efficiency' isn't it?
The day of the install, Bob and his dad (since retired) came in and removed the old furnace and installed the new one. No fuss, no muss just efficient. Great people to work with and wonderful service. Bob has been doing my yearly maintenance ever since. Highly recommended.