Kawasaki Ninja 650R - Next Level of 250R

I thing you have to change your 250r motorcycles to better engine such as 650cc like Kawasaki ninja 650r. Why? I know that Kawasaki 250R is fast enough for your daily activity even for woman, but sometimes, we need more motorcycles power and we want to get more fast bike, so what should we do? buy a racing parts? or change your motorcycles to the next level?
Kawasaki 650R is medium class of Ninja