Which bike would you think would be better for me? I was looking at Ninja250, 500, and 650? I've never even rode a dirt bike before but I do plan on taking some classes before I buy my bike. A lot of my friends have been giving me hell about thinking about buying the 2008 or 2009 Ninja 250 saying its to weak. What do you guys think and do you have any other recomendations?