I am currently shooting a nikon d40 with a 55-200, 18-55, and 50 1.8, and I mainly shoot high school sports to sell the photos to parents. I also have an sb-600. I pretty much can't stand having low-end gear, but I'm a starving college student so cash is tight. I've been doing pretty good with what I have, but I know my gear is limiting me. I currently have $800 to spend and I'm not sure if I should spring for a new body (d90), or a sigma 70-200 2.8. My plan is to get one, then use it to earn money to buy the other. Which one should I buy first and why? I'm leaning towards the lens, just because shooting football with an f5.6 has been (nearly) impossible.