I think we'd kill GB. Their offense matches up almost exactly with what we are good at - great QB (and poor OL) with good WR's. Well, we have excellent pass rushers and defensive backs.
Where our D has holes, GB has nothing - they have had almost no production from the TE position, their RB corps is decimated. They don't have the personnel to stress the middle of our LB's like NE can, and they don't have a running game like the Texans do to keep us out of nickel.
Defensively, they are maybe slightly better than average pretty much everywhere. They have had a ton of injuries there too. apparently they will be getting Woodson back this week, but I'm not sure how much he has left in the tank.
Atlanta - no problems there. If not for some uncharacteristic interceptions by Manning and a phantom Falcon fumble recovery, we win that game in Atlanta. I have no issues with them.
SF and Seattle - I don't know what to make of these teams. The defenses these guys play is nasty. I don't think their offenses are all that great though, so this is a case of what can Manning do. Gotta believe our D i better than their O, so we've got better than a punchers chance.