Anyone who tells you that you can outgrow a 600cc bike is a dumb ass. You have to be a straight pro rider to be able to ride a 600cc to its maximum potential. None the less even ride hard on public roads. At first when you get on a bike 40mph feels like 80mph. There is so much wind hitting your chest and its pretty intimidating. I would just ride around your neighborhood for a few weeks. Get used to the clutch, speed, leaning, emergency stops.
Now a days a 600CC bike with a good rider can go 10's in the quarter mile. Does everyone exactly know how fast that is? That is faster than cars that have 500 horsepower.
Ive been riding for about 6 years and have had almost every CC bike you can think of. A 600, 636, 750, 1000. Personally a 600cc is a lot more fun to ride. The liter bikes are no joke, they will put you on your ass if your not careful.