I drafted Volquez thinking I was getting a high k, high upside starter. I dumped him a few weeks ago. Of the list you mentioned, I'd lean Danks as well.
Though his play so far doesn't justify it, I would actually take a shot at Reynolds. He's a very, very streaky player and his whole season so far has been a giant cold streak. I think it's only a matter of time before he goes through one of those stretches where he's one of the best players in the game. I also like Snider long term this year, but while he's in the minors it's unlikely anyone will be quick to pick him up. In the meantime, see if Reynolds can get things going.
I don't think you need to add any pitching, but if you do want to go for a pitcher, Danks is probably the way to go. A case could be made for Lowe--who is aptly named for being "low" risk, but also "low" reward. He will contribute, but you're more likely to hit a home run with Danks, who gives you much better K upside.