I have a Nikon D750 body, with the 70-200 2.8 and the 200-500 5.6 Nikon lenses.
The two options I can think of are:
(1) Buy a 1.4x or 1.7x teleconverter for my existing D750 (FX).
(1.1) Approx. Price Nikon £400, Sigma £200, Kenko £100
(1.2) teleconverter add more glass, and may decrease sharpness and image quality. But they are significantly cheaper.
(2) Buy a D500 (DX).
(2.1) Approx. Price: £1,700
(2.2) The D500 will be better quality, may be handy to have a second camera with me to speed things up, but significantly more expensive.
There's obviously a huge price difference. I can afford it though, but at the end of the day it's hard earned cash, and it can always either be spent on better things, or simply saved.
I would like extra reach for wildlife photography. I do not make money from my photos, yet, but perhaps fit in the 'very keen professional hobbyist' category, if you can imagine such category.
So what I'm trying to conclude is:
(*) Is it worth buying a DX body to get that extra reach, or shall I go for teleconverter instead? And shall I simply buy a more modest DX body instead?
(**) if teleconverter, is there a huge difference between say Nikon and Sigma? And is the 1.7x worth the aperture and light loss for the extra reach?
Your thoughts and opinions are much appreciated. Thanks in advance.