Just another point for consideration..

Where are you planning to fly?

At a club only or also in the local Park?

A 450 can be a dangerous machine and can hurt you if out of control

a 500 or 550 is much more deadly and could kill you.

I fly my 450s in the local park but pack it away if there are too many people around..

I'd never fly a 550 anywhere except a controlled environment like a club... 

Just to be safe...