I have a few questions, is it better to go with say the canon 70-200 IS with an extender, versus an lens that has a longer zoom but only f4-5.6 or something like that? I know I can't afford a 500mm lens. So do you go for better quality over zoom length?
IMO PeterP had fun spending your money :-) However in a sense, he has also answered your question: "I'd really consider the Sigma 120-300 F2.8 EX HSM. Optically excellent, fast focusing and you have a good zoom range in it. It also works very well with a 1.4 or a 2x TC's. Giving you a 420mm F4 and a 600mm F5.6. It is one of the lense most attached to my camera
You can basically cover 17-600 mm with just two
I'm more concerned about carrying all the stuffs than taking pictures overseas... and be a magnet for pickpockets
I am a bit wiery from some of the things I have read about using non-canon lenses, obvioulsy lots of people do use them with no problems, yourself included I asssume? Do you ever have to worry about a Sigma or Tamron lens not working probably with a Canon?