Heating Contractor work well done within budget - respond

“About a month ago, this company name was brought to my attention by my rental house manager for consideration to replace a malfunctioned old gas furnace. The unit brand name is Amana and the price was about 40% off the new price (because this unit was a return from a previous owner due to their upgrading to a higher end unit, I was told). The guy quoted a price for me and had stuck to the limit. The timing for the installation was given to me and they came the same day as promised. I haven't heard any complaint from my tenant and I assumed that the unit is working properly.”