I have the same motor on my HK450. Works well. It's my first heli, so I don't really have an idea of how powerful it is compared to others...but it seems to have plenty of power.
I've been using a 50-65A ESC
Works great and is cheap. After a fairly hard flight (well, hard by my noob standards), it's not even warm.
EDIT: By the way, what made you go from a 500 to a 450? not saying it's a bad thing...but your build list will almost completely change based on that 450 you have picked out.