dont fall into that 'bigger is better' crap. Anyone trying to tell you 'you'll outgrow it' or 'youll get laughed at' is feeding you a line.(i dont own a 500).
The EX500 is a great platform for learning. You can do alot on a smaller bike you cannot do on a 6, and it is far better for building your skills (the higher performance bikes help to isolate the rider from feedback, critical in skill building).
Anyone can twist a throttle for speed, but its a lot more fun to acquire speed through your own skills than through purchasing horsepower. Go to any track and youll see ex250s, ex500s, and fzr400s pouncing the 'real' bikes.
I dont want to dissuade you from a 6, i just wanted to point out that not all cyclists think displacement=speed. I learned ona 750, traded down to a 6, and am considering a ex250 as my next ride. And when someone laughs at me, ill be comfortable in knowing i can outride the moron who thinks that displacement indicates skill.