I've been throwing the idea of upgrading my camera for XMAS. I currently have the Canon Xsi with the kit lens and a 55-250. I'm currently using it for family photos and really just on auto but I'd love to learn more as the kids get older. I'd like to stay with a Canon camera but am wondering what models to look at that will be that much better than the one I have. I'm specifically concerned with improving speed and low light pictures. Or do I just get a lens that will perform well in low light settings? Thanks for any help!