I don't know if it is wise to buy steem power.
The best investment tip is: 'diversify'
As to voting: You can check your voting power on steemstats.com ( thx @jesta )
As far as I understand: The votes don't only add up, but factorise somehow.
That means your upvote can have a bigger effect than just 0.000001 cent.
that is the part that I didn't understand very well
http://www.steemdollar.com/dollar_per_vote.php?name=felixxx
This is, what my vote is worth individually.
lol this is worth of my single upvote $ 0.00048774405355311