I will be backpacking in South Africa in a few months and will visit Kruger while there though I am having trouble figuring out what my best budget option is for a lens. I have a Rebel XS and as I am backpacking I am concerned with budget, weight and theft. Since my camera has a 1.6x crop factor, I am debating if I'd be OK with an EF 70-300 IS USM. I also have a 17-85mm and decent P&S for wider shots on safari. The other lens I am considering is the 70-300 DO. I'm not sure I need the 100-400 on a crop sensor, and would prefer to not stand out so much with a white L lens, nor am I thrilled about the prospect of losing such a lens. I would probably buy used and sell upon my return, though should it go missing I'd much prefer to lose the standard 70-300 than the DO. I could also perhaps get a 1.4x Extender. Would anyone strongly advise not to use either (or both) of these lenses?