Tim's already given you his conspiracy theory about why Travis Buck means the Astros are preparing to move to the American League. I offer a little synergy in my breakdowns of Buck and Stavinoha's backgrounds over at SB Nation Houston. But, I wanted to talk about the signings here in more general terms.
The short of it is: I like both moves.
They're not going to win the Astros more games next year, but they both bring something to the table that this team lacks. Neither are perfect players, but that's why they were freely available for Houston to go get.
Buck, while he's not an inspiring choice as an outfielder, could be one of those buy-low, high-upside options. At this point, I think the fantasy that his power will someday come around is gone. But, as a doubles hitter with a good batting eye, he could hit .280/.360/.420 pretty easily. Only one Astro had an OBP higher than .360 last season and that was Michael Bourn.
I don't think it's a foregone conclusion that Buck will win the starting right field job, but we really don't know what he's capable of. He hasn't been given a chance to settle into a lineup and play regularly and he's at an age when he should be hitting in his prime. Even as a fourth outfielder, he'd be valuable.
Stavinoha is a little more problematic, but there's no questioning his power. He's hit for power at every minor league level but wasn't successful in his short major league stints. I'm not sure he wins an everyday job, but if he's the fifth outfielder and pinch hitter off the bench? That power becomes an asset. Plus, he could spell Carlos Lee at first or J.D. Martinez/Brian Bogusevic or Buck in the outfield.
Houston isn't a very patient, OBP-friendly team and they surely don't have a lot of power. By picking up each of these guys on small deals, the Astros are buying a couple of lottery tickets that may or may not impact the 2012 season. We can't hope to sign Jose Reyes, but we can hope that the Astros continue to pick up interesting guys who can add value in different ways.