I voted Carolina. I think Seattle goes 8-0 at home again (though Tampa [streaky, weird team] and New Orleans [even bad Saints teams can win anywhere] concern me slightly). Since Qwest/Clink opened in 2002, the Seahawks have had four 10+ win seasons. During those seasons Seattle had a combined home record of 31-1, with the only loss coming to a bad but dangerous Saints team (2007). Add postseason home games by those four teams and the record climbs to 34-1. When Seattle posts 10+ wins, they don't lose at home, period.
As far as the division, all Seattle needs to do is play focused, mistake free football and they will have a very strong shot at 6-0 in the division. Their four most mistake prone games last year were all in division play (the three road games + Rams at home), and they still went 3-3 with a massively positive point differential over those six games despite that.
Losing to Altanta would suck a lot. But not as much as losing to the Colts. Both are at 10am, and both worry me. In the case of the Colts, it's not because they are a good team, but because they are exactly the kind of team that beat us at 10am last year: bad, but clutch as hell. Plus if the Colts win then the idiotic Luck hype-jobbers will never shut up about it. It would please me more to beat the Colts 60-0 than to win at SF 60-0, though obviously I'd like to win both games. Something about the Colts just gets under my skin, and I'd love to see the Seahawks make a statement when they face off.
Carolina scares the hell out of me too, though at least with Carolina we match up very well against their offense. I expect a very tight game. Their defense was on the rise and that was before they added two of the better DTs in the draft. Carolina has drafted well the last few years and the team finally gelled at the end of last season. I think their front office is flying under the radar.