Yepp it doesn't get much better than a rmz450. I brought a brand shiny new 2012 model myself, 4 years later it still runs like a dream an thats with about 70hrs of mx track time on her... as long as you keep up to date with factory mechanic services and look after your valves. The new 450 4stroke will last u a long time. they're the best bike for even a beginner/amateur rider to learn on and plus a 450 is the power you need.
Go Ken roczen