Is $1,800 to move the furnace directly under the trunk a fair price?

I am currently looking to replace my furnace and am getting conflicting information from HVAC estimators regarding the necessary work. My 1300 sqft home in Calgary, AB, Canada, has a 100K BTU Lennox G20 furnace from the 90s. I believe the furnace was moved about 15 years ago, and it now has a new plenum and duct that makes a 90-degree turn under a joist and return duct before connecting to the bottom of the main trunk. Two companies have said the furnace is fine where it is, but one company insists it needs to be moved directly under the trunk, claiming that not doing so could cause premature wear and void the warranty. I don't want to pay the extra $1800 to move it if it's not truly necessary. My research hasn't confirmed that the furnace needs to be directly below the trunk, and I assume correct plenum/duct work should provide adequate air pressure. Air pressure seems fine currently, but I have nothing to compare it with.