I have a 2 story house with a loft that overlooks the high ceiling living room. The heating and cooling are very uneven throughout the house. The unit is upstairs & the thermostat is downstairs by the door to the garage. The furnace is gas. I have ceiling fans in most of the rooms. I have received conflicting info on how to resolve the issue. I need to replace the coils in the a/c due to a leak, so I want to take care of this at the same time. The house is 7 years old in Austin TX. What are my options and the pros and cons of each? Thanks.

I forgot to mention that, due to the way the house is designed, the duct work is inaccessible so changing that is not feasible. :-(

Sorry, but it sounds like your system was poorly designed. You would have to gain access to duct work and most likely add more duct work with electronic dampers and themostats to control separate portions of the dwelling. Without doing this, you have no real way to cure your comfort problems with the single heating/cooling system. Only other options would be to add some other sort of heating and or cooling epuipment in the areas of need. Electric baseboards, window ac or mini split ac/heat pump may be an option, but without seeing the set up first hand, there is really no good advice to be given here. Hope you find a contractor that can come up with a solution.