I really don't think the Seahawks would be a bad matchup. Our defense is great against the run and mobile QB's. Our best performances of the last two years have been against RG3 and Newton. Yes the Seahawks are better than those offenses were but I still think we'd hold up better than against New Orleans, Detroit, or Dallas. Detroit is inconsistent so I doubt they make it, but they're also the type of team that can be the spoiler for one of the top teams like Seattle, and then blow it the next week.
The game would still come down to turnovers and officiating, as both of our losses did this year. This past KC game was the first time this year that a team has correctly been flagged for offensive holding and DPI against us, and it made winning impossible for the Chiefs. If the Seahawks can do whatever they want to our pass-rushers and receivers like most teams do then it would be a game, but I still think we'd win. Unless of course we're -4 in turnovers.