Hi Les, I shoot with Canon 300d, 350d and now 30d with 70-300mm lenses. With the Canon 70-300mm IS I need to add extension tubes or the Canon 500D close-up filters to shoot within 1.5 metres to get a 1:2 or better magnification. With the Tamron and Sigma lenses of the same zoom specs, they have switches that allow focusing from around 50cm for a 1:2 magnification. I still have a spare 350d and the Tamron 70-300mm lens as well as a Sigma 500 Super DG flash with a Stefon omnibounce head, which I'm will to let go for S$1200 if you are interested.
Richard