A few days ago for my birthday I got a Nikon D40 DSLR. It came with an 18-55mm lens, a 55-200mm lens, and a 2gb SD card. However, I have the option of upgrading to a Canon Rebel XSi. From the same store as the Nikon (Costco), the Canon was a few hundred dollars more (it is $799, and I would have...