Hi rosey,
Had the 450 and the 550, also been on gruntunbergs 501. The 501 is alot snappier off the bottom, the 450 is a lighter feeling bike (even if it is`nt) with smooth power. The best of the bunch i think is the 550, loads of useable power, same weight as the others and even with that amount of power its not a tiring ride. Pop in the chat room when you see me in there we`ll talk more.
brookester