I currently have gas ducted heating (Bonaire product #5430052) and am looking to have cooling added on. Is this possible with this system or is it more cost effective to have a whole new system put in?

I live in a double story townhouse, downstairs there is one duct in the living room, and two ducts in the kitchen/ dining room. Upstairs there is one duct each in the 3 bedrooms.

What would you recommend and the approximate cost of the system or would you need to come out to look?