I am trying to determine the best super telephoto zoom for my meager budget. I would love to hear any pros/cons on any of the following lenses. Sigma 50-500 Sigma 170-500 Tamron 200-500 (currently offering a rebate) I already started another thread on the nikon 80-400 which is why it isn't listed here. I am currently shooting my D80 with the 70-200vr + 1.7TC, but want to get more range. So far, I mainly shoot wildlife and birds, with the occassional kid's sporting event. I am fond of the idea of a zoom, but am not entirely opposed to a prime (if the difference is that great). If I had unlimited $$$ I would get the 200-400VR and/or the Sigmonster 300-800 (in my dreams). I am a newbie, serious amature, but aspire to something more. THANKS for your input!