I have a 3,000 sq ft home...two stories...four bedrooms and two baths upstairs...downstairs is very comfortable but upstairs has been traditionally (last three yrs) warm tot he point I need window A/C units in bedroom windows to supplement central air. I've been working with a local Carrier dealer and have built a true level of trust with him to purchase a system. We've done several things to rectify current cooling problems upstairs to include blocking downstairs returns to force upstairs (one in the hallway) return to pull ot air, increased insulation in upstairs attic to reduce hot air pushing into bedrooms, and two thermostate exhaust vents to push more hot air outof attic. I'm at the point to buy a new system and have a quote for Carrier Infinity system; Air Handler: FE5ANB004 and Heat Pump: 25HNA636 giving me 16.6 SEER, 12.6 EER, & 9 HSPF. He believes this will take care of my problem but pauses when I ask for a guarantee to this having to fix my problem or come take it out! he says he could fix it for sure with "zoning" for an additiona $0...not sure what to do?