You'll be more than happy with the power of the 600. It has a lot more actual performance than it's exhaust note would suggest. Like Darryl said, it isn't the most powerful blower out, but it's right up there and it will more than hold it's own for all but the worst clean ups and even then, it's no slouch.
My only complaint is that the shoulder straps want to slide off my shoulders too easily compared to most other blowers, and I'm not what you'd call round shouldered at all. I did buy the optional chest strap for mine and it made a big difference. They are very light, have an excellently designed pistol grip throttle, and they do far better on fuel than the big 2 strokes do.