I'd forget about cameras that don't exist. The 6 D sounds perfect but I don't know what lenses you have or what else you enjoy photographing. If your really only buying for one trip then rent. A 70D may be fine enough or if you also do action the 7D2 would be obvious and last probably as long as your 400D
What ever you do good luck with your choice!
What ever you do good luck with your choice!
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