Wahle technically is not a free agent. But he has a huge roster bonus due to him next month so that the Packers will likely cut him, making him eligible for free agency. It's the same thing with Kurt Warner and possibly Ian Gold (although I'm not sure exactly of Gold's contract details). Muhsin Muhammad is in the same boat, but I don't consider him a true FA candidate because I think there's a pretty good possibility that he and the Panthers will restructure before March.
Darius would be a good pickup, but probably one that will cost a pretty penny. I would prefer that if the Falcons were going to sign a big name FA that cost quite a bit, they would make it worth their money by spending it on a position like OL, WR, or DE, which are positions I think are a little harder to fill via the draft than safety.
Kenoy Kennedy, Dexter Jackson, and Dwight Smith are 3 more safety FAs that would be worth going after. Smith and Jackson are probably more likely options due to their connection with McKay (he drafted both in Tampa), while I suspect Kennedy will be re-signed by the Broncos before free agency hits. But I would love to get Kennedy. He's a fierce hitter and enforcer in the secondary, something I'm desperately hoping the Falcons can get this off-season. Also I'm hoping for the possibility that a guy like Shaun Williams or Lance Schulters is cut this off-season. I think both would be good fits here in Atlanta. Schulters would be a good fit due to his experience in San Fran, but he will be 30 this upcoming season and has struggled with injuries throughout his career.
"Vincere scis, Hannibal, victoria uti nescis" -- Maharbal, 216 B.C.E.