Keith
The best camera is one that still works!
$2400AUD is an awful lot of money to spend if you're not sure. Why not rent?
The camera will generate a small income over the year as has done my M8 up until now which cost me more than twice as much, so $2400.00 three years on is not a huge amount compared to the Leica.
I don't actually doubt that the D700 will be more than capable of doing what I need and having had a D70 for several years (sold it) I have a high opinion of Nikon DSLRs generally.
My main consideration will be deciding the future of the M8!