I think Erstad will be neither stud nor dud this year, but a middle-of-the road of. You could do worse, but if you can upgrade, there's no reason not to. I'm not quite ready to lower the boom on Cedeno yet. He's never been a quick starter (now that's an understatement...), which is frustrating, but his speed potential makes it worth hanging on to him a bit longer.
Chicago's right about Kearns - though I love the way he plays, the playing time situation in Cincy is completely up in the air. At the moment, it looks like he'll keep seeing at bats, but if he slumps, the odds are good he'll be sent down.
And Alou is truly a stumper. Finley is certainly a solid player, as Chicago said earlier, but I'd wait just a little bit longer before giving up on Alou, even though it's risky. For one thing, your of is solid enough that you can afford to be patient, and for another, Alou wants to play and play at a high level. I'd give him the chance.
You might also try shopping some of your outfielders. Hunter, Cedeno, Kearns, or Erstad might all bring a decent return, and perhaps you can package them into a deal that clears roster space, allowing you to grab Finley for free.