In a sense yes, Steem Power indeed plays a big part in increasing a posts visibility. To be more specific the upvote worth (rshares) it contributes to the post.

It is no hidden fact that the more Steem Power you have the more your upvote worth will be. If say the worth of your upvote is at $10-$15, then your post will go straight into the "Hot" section or even "Trending" on the not so used steem tags. A post of $50-$100+ is often than not placed under the "Trending" section which increases more your visibility.

However that is not all, One's Followers also plays a big part on a posts visibility due to resteems. The more resteems you get, the more visible your post is.