I am slowly raising the specs of my bird photography equipment. I have replaced the 100-400 with the 100-400 Mk2 and have acquired a 1.4x Mk2 extender. I am still using the 7D body but want to be able to use the extender in AF mode as I find MF difficult while hand holding the 7D. I am trying to decide between a used 1D Mk3 and a New 7D Mk2. Price is not a real concern but I am concerned by the amount of negative comments regarding IQ and focusing on the 7D 2, or have these issues been overdone? I would welcome advice please. I am not interested in going FF and would not wish to go any higher in price than the 7D Mk2, currently £1420. Thank you.