not my scene Richard, look at what guys doing motor sport are using and include Derekb in that.(also search pbase) I suspect you have an irreconcilable problem between performance and budget. In the long run you will only want top quality lenses and will have wasted cost of any cheaper substitutes you buy in the meantime. Also don't forget converters go between body and lens, so more changes, more sensor dirt.

Are you familiar with the review sites eg
http://www.kenrockwell.com/nikon/182...s-55-200mm.htm
http://www.bythom.com/18200lens.htm
http://www.ephotozine.com/article/Ni...DX-VR-f35-56-G

http://www.nikonlinks.com/sitemap.htm gives all reviews by lens