I have a canon eos 7e and a quite nice tamron 28-200 lens (which feels like a 300 lens?). now I'm thinking about buying a used longer lens. I have about 300, 350 bucks at most to spend and I hate nothing more than those photo salespeople who know ten times more than I do and always try to talk people like me into buying crap. so that's why I'm asking for advice here> do you have any recommendations? what should I look into, what can I expect (will I get a used 600mm lens for that money?) ... oh ... and pitfall-stories are very welcome. I can only learn.