eventually i would probably like to end up with the 400mm and a zoom in between 100-300 to fill the gap
i am thinking 300mm f4 L with a TC too maybe to start,
That is what I use for 99% of my wildlife stuff now.
Before that I was using a 70-200mm f/2.8 with TCs but it was just way too shot 99% of the time.
70-200mm is actually much more fun for landscape and portraits.