Kenko pro 300 on D70 + Sigma 50-500 ?

Hi,

I have the Nikon D70 body.
I'm looking for a used Sigma 50-500 -
and after reading very good comments on the Kenko Pro 300 -
I though to order one from B&H.

but just before I make the call,
I know they have X1.4/X2/X3 models,

1. Does they all support the AF and other camera functions ?
2. Any picture quality diffrences between those three ?

thank you much,
Gal.



(would get the Nikkor 80-200/2.8 one day also.....)