If you can find a good condition 1DmkII, it would probably be the best camera for the least money. I sold mine about a year ago to get a mkIII, I think I sold it for $850, might be less now. The 1DmkIII can be a good buy too, though if you can find a reliable one (where the AF works well) then I'd think it would be more expensive than a 7D. Compared to the 7D, the 1DmkIII has a little more noise in the higher ISO range, but more detail. I think the 7D just has stronger noise reduction, which sacrifices fine detail. So in that respect, I think the 1DmkIII has a little better IQ, the 1DmkII would be a little less than that, you probably wouldn't want to shoot the 1DkmkII any higher than 1600, better to keep it at 800, the 1DmkIII is pretty good at 1600, fair at 3200, the 7D is less noise at those high ISOs, but less detail too. Sounds like they may announce a new camera soon, probably a 5D update, so seeing what that will look like may change your plan, but if your budget is your main concern, the 7D or maybe a 1DmkII would be your best bet in any case.