A 250 is plenty of bike for anybody. My buddy rides a 250f and its almost as fast as my cr250 plus gets great gas mileage. The only need for a 450 or even 250 2-stroke is in the dunes where more power is needed due to the deep sand. You will be happy with a 250f and if you want a lil more power down the road you can get a big bore kit or even do an pipe and silencer.
Check out 250 two strokes as well they're very fast and much cheaper to buy and maintain then a four stroke