I thought nano was a term for under 10 gallons, so I'm not sure what you mean by nano tank unless all your fish have more than ten gallons apiece? In which case, why change anything?
I am tempted by the Fluval chi - very much so, but at the moment they are about $100 here in South Africa so its not an option for me at this point. Maybe one day. Also keep in mind the fluval chi is open top so the water apparently evaporates very fast.