I've been watching the Nikon D7100 or D700 for low light with some interest. I have a D7000 with some DX and FX lenses which is being replaced by a Sony A7 based system for general wandering around and travelling. However, I like to shoot (mainly classic) motorsport and was going to keep the D7000, 70-200 f2.8 (Sigma) and 300 f4 (Nikon) and 1.4x teleconvertor purely for motorsport purposes. I am wondering if it would be worth selling the the D7000 and getting a D700 for this? This wouldn't cost a lot of money, and I don't want to spend a lot of money for something I do a couple of times a year at most. So, for the 300 quid difference between what I'd get for the D7000 and what I could get a D700 for, would it be a good move?