ive got a xsi and im looking at more lenses to get, but i dont know what i want, so what do you think is a good lens to have in the bag. right now i have the 55mm wide angel that came with the xsi, a tamron 70-300mm telephoto and a Canon EF-S 60mm f/2.8 Compact Macro, so my question to you is what else should i have in the bag. id also like to add that i prefer canon glass, also what is a good shutter release to pick up