Well, that's my current dilema. Let me try and explain...

Bought this house last year, moved in in July. 2 story house, approx. 2200 sq. ft, 3.5 ton Bryant central heat (gas) and air, house built in 2000, so 5 years old. 2 bedrooms, 1 full bath, half bath, and 400+ sq. ft bonus room above the 2 car garage on the second story. The problem is that the upstairs bedrooms never really cool. The unit can literally run all day and freeze the downstairs out, but these bedrooms get minimal airflow from their vents. In TN so in case you don't know it can get 90+ easy and always high humidity in the summer and fall. Last year I just bought a couple of window units for the bedrooms figuring that would be a bandaid until I decided what to do with the central AC.

So I finally started calling around to some HVAC companies for some suggestions and quotes on getting this problem solved. Had the first guy out this afternoon and he suggested zoning the system. Real nice guy, and he did a thorough job of explaining everything, but I'm still not sold. He'd replace the thermostat downstairs w/ a new digital one, and then put a new digital thermo. in the upstairs hallway. The one bedroom that really doesn't cool is on the side of the house where the unit is. He explained that the duct work runs under the house to the other side, then up, and then back down to the upstairs side the unit is on. This bedroom that never cools is the last vent on the chain. Literally, you can feel no airflow in this room's vent. I guess my thought is if the unit was running, and it was also running downstairs (i.e. the damper was open to the downstairs vents) then wouldn't I still be facing the same problem? Is the benefit that I can set the downstairs thermostat to a higher temp so it doesn't run much, then set the upstairs to a cooler temp to make it (in theory) force all of the air from the unit upstairs (and hopefully force air to this last vent) and then cold air falls, so that would help cool the downstairs?

I know I'm probably babbling here. I guess I just wanted to get a general consensus on how people here feel about zoning. I thought my only option was to put in a second unit for the upstairs (which he said would take on another $3500 to the price) and that he didn't recommend it. He said that would cause problems with the 3.5 ton unit now cycling on and off too much because it's trying to cool way less area than it's designed for. I'm just afraid I'm going to drop ~$2500 to zone a system and it not work.

Any thoughts?
Thanks in advance!