5D3 would be good as an all-purpose body but you'll lose that extra reach. An ISO of 12800 I think is still usable though so you can add extra reach through extenders but it will set you back a lot of dollars I imagine. Anyway, I've browsed through your bird shots and it's very good and educational.
The 5D3 actually has more reach than the 1DX. Both are full frame bodies but the 1DX has less pixels. I survived with the 5D2 so follows my being critical with the 1DX.
TCs are ok but you lose stops of light and AF becomes less quick and decisive.
Glad you appreciate the hardwork put into making them. They often get stolen by locals for their advocacies. They often point to budget problems but they have cash to pay their employees, suppliers, vendors and other people.
Often times they are just plain uncourteous. Upbringing I guess.
Which reminds me. I'll start posting images 800px and smaller.