If I am not mistaken, this lens cost about $200. The Nikon teleconverters all are about $500 each. The Tamron teleconverter is about $150. But even a 1.4 magnification will cause you to be shooting at f/5.6-8. And, my suspicion is you are shooting a body which will not autofocus at f/8....Also, my experience with TC's which are relatively inexpensive is that one gets quality which may not be acceptable. You did not state what body you are shooting.

To get a telephoto lens beyond 400mm generally becomes expensive. But, see how you like your new lens and then decide what you want next...like all the rest of us...

And, you have chosen to ask the questions on this thread, so that is where we will go..

http://nikonrumors.com/forum/topic.php?id=5486&replies=20#post-128139

I found that the Kinko Pro 300 works on Nikon and Sigma lenses. I have tried it on the Nikon 70-200 VR1 .. Nikon 12-24 ... Sigma 50mm macro and the Sigma 24-60. Not that any of those are what you asked about however it might be worth a trip to the camera store for a try.

You are going to add 1 stop to the aperture though, so it will need to be fairly light for you to use the lens.

There is the problem with the rear element hitting the TC, so put it on VERY slowly and try to feel if they touch.

Sorry Sary this lens is not really suitable for TCs

http://nikonrumors.com/forum/topic.php?id=12381

i have bought tamron 70-300mm f4-5.6 .what TC would you suggest please ?