Hi there, I've got a 20D which I'm happy with even though it might be considered old these days. As for lenses, I have the Canon 18mm-55mm Kit lens, Canon 28mm-105mm F3.5-4.5 and while I have no major complaints in the optical quality of these cheap lenses, I hate the wobble on my 18-55. Any suggestions for a low cost lens that will replace that one and be built better? Hows the Sigma 17-70? It looks like it would be decent from the reviews.