My thinking is that if your still growing then why spend $650 now when you'll have to spend another $700 (inflation) in two years? Sure you could buy a bigger bike but if the fit isn't right then your going to uncomfortable until you grow into it, and then because your uncomfortable you won't ride it so now you have a $650 piece of garage art. So why not save that money and buy a lower costing $350 range bike? Or are you willing to shell out $650 now then later in two years shell out another $650? Also at your age, you may become completely uninterested in cycling in 1 to 2 years due to getting older, thus wanting a car so you can take a girl out...most girls don't really dig guys on bikes!! They want a guy with a car. I went through that same thing, in 1976 (I was 19) I bought a $2200 Trek TX900 and had it for a year, but the girls just didn't understand why I had a $2200 bike and a $800 car, so I sold the bike and the car and bought a nicer car.
Anyway just one morons thought.