what is your height n weight? Do you plan on riding in areas that have huge hill climbs?
Sideways is the way forward,One thing I had a hard time learning coming from strictly sportbikes...
Dirtbikes don't always point in the direction you're going... It took some getting used to...
-BIG DAN
well then, total power is not a concern if not hill climbong and given your weight. Your 6-1 makes any bike fit your body. So, i would say if you want a bike you can keep and grow with then get a 2st 250-300. If you really think you need a 4st then a 450. Yam, Hon, KTM all have been making off road trail bikes in 450 for a while so you can find one in your price range. The 2st is more a KTM or Yam thing for a good 250 for off road.
2st will be lighter, less maintenance and start easier.