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I agree with most of the folks here. I don't see a difference between #3 and #4 other than the background, which has nothing to do with the logo at all.
The spark is nice, but it big and alone by itself on the top of the logo doesn't seem to be working. I would "half" the spark horizontally and place it between the ascenders of the H and K, resting on the h-s-p-a-r.
And I agree that it still needs to be simplified.
