Camera people help

[angie_phoenix]

Would it be better to wait to be able to afford a Nikon 70-200 or would a similar sigma or tamron be a better choice based on being about 900 cheaper?

All 3 lenses are on this page http://www.amazon.com/s/ref=nb_ss_e?url=search-alias%3Delectronics&field-keywords=nikon+lens+70-200