Well, I have 40 reputation, but only8 SP! (and I did upvote you)
Steem Power seems quite expensive for even a small upvote value, and I have never really thought about buying any. I do convert almost all of my earnings into SP, but haven't earned enough on my posts to do so.
I don't really know much about reputation, is 40 very high? I don't feel like I'm doing enough to be a high reputation member. I am active in the community, but am still very small, about 1/3 your size.