I'm still using my Nikon D50 with a Tamron 28-75 f2.8 I like to photo events at the local speedway, but I get in trouble when I run out of light. I have learned where the track slows down, and where there is more available light, so I can bet a few shots that are at least viewable. I can only do this by lengthening the shutter time, as apeture and ISO are already maxxed out. My outfit is capable in broad daylight;when the sun goes down, my problems start. Now that you know this, I would really like to have a D700, and a 70-200 AF-S to mount on it. Unfortunately for me, that ain't in the cards. What I have determined what I can do is either a new D90 or a used D300. I understand these cameras use the same sensor, but the AF set up is different. Am I mis-informed here? The lens would be either a new Sigma 70-200 HSM or a used Nikon 80-200 AF-D. The tradeoff here is better optics and quality vs. speed of focus. Speed is more important in this application, so I would lean toward the Sigma. I was also wondering about getting a Nikon 50 f1.4 and keeping the old D50, and see if there is any room for improvement there. I have my doubts for 2 reasons: I would have to stay at 1600 ISO, and that lens would multiply the inadequacy of the sensor in low light, and an even narrower DOF. So, any thoughts about something else I could do. I am not a professional. Hell, I don't take in penny one, although I probably could. I cannot justify tying up 3-4k in camera. Maybe I can't afford Nikon, and should look for another brand?