You can take the position of "achievement isn't a feeling of power" if you'd really like to, in which case I simply say find and replace all prior uses of "feelings of power" with "feelings of achievement" and the argument still stands. I'm happy to use whatever definitions you want. Taking joy from your success in doing things (whether you refer to it as achievement or power) is simply not an valid ethical justification when it is at the expense of violating other peoples right to control of their possessions.

I don't know that the argument stands with "feelings of achievement". I agree that you can't justify a moral infringement by taking pleasure in it, but upthread you were trying to distance the motivation from virtuous ones like curiousity and activism. Being driven by achievement is absolutely a virtue. I'd argue it's the same virtue that drives curiousity, and you've essentially just said exactly that ("the feeling of solving a puzzle is a 'rush of power'" s/power/achievement).