Rather than having these spread out through various comment threads, I'm going to post the scenarios in which the Sounders will advance to the knockout stages of the CONCACAF Champions League right here for your viewing pleasure.
Since Monterrey and Comunicaciones both are at 6 points, quite often in scenarios they will be interchangeable. Rather than type a bunch, note that Montercaciones and Comunirey represent either team, but never the same team, if that makes sense. I've also, for your convenience, indicated whether the scenario is achievable in one game in situations where it is.
THE SEATTLE SOUNDERS WILL WIN GROUP D IF:
*They draw or better against both Monterrey and Comunicaciones.
*They beat Montercaciones and Comunirey draws or loses to Herediano. (one game)
*They draw Comunirey, and Monterrey and Comunicaciones both lose to Herediano
THE SEATTLE SOUNDERS WILL ADVANCE IF:
*Any of the above
*They draw Monterrey, lose to Comunicaciones by two goals or less, and Comunicaciones ties with Herediano
*They and Herediano both draw Comunirey.
*Herediano beats both Comunicaciones and Monterrey (as long as SSFC maintains a better GD than Comunicaciones and Herediano) (EVERYBODY HAS NINE POINTS!!!)
I believe that's it, though I may have missed some. Yes, it is indeed mathematically possible for the Sounders to lose their next two games and still advance. It's also mathematically possible for Herediano to win the group, though, so take it lightly. We control our own destiny, though, and could win the group in a number of ways without help. The best thing I think would be to beat Comunicaciones and hope Monterrey doesn't bring their A-game against Herediano. That would clinch a SSFC victory next Tuesday regardless of what happens in Round Six. Two draws would also win the group.