For as in Adam all die, so in Christ all will be made alive.

Dewey,
I was hoping you would say that.
I've thought about the infralapsarian/supralasarian debate quite a bit since doing some research before attending a debate between Richard Mouw and the president of the Protestant Reformed Seminary on the topic of common grace.
I've gone back and forth since then as far as which I think is the best position. Recently, I came across an article by Alvin Plantinga entitled "Supralapsarianism, or 'O Felix Culpa'". After reading it I am pretty firmly convinced that I am a surpralapsarian. He approaches the problem from the standpoint of the problem of evil. His discussion, in addition to dealing with supralapsarianism, also sheds a lot of light on why bad things happen and, if they understood his argument, would provide solace to Christians who are suffering.
It would be difficult for me to summarize his argument because Plantinga is a pretty tight thinker but you can find the article at the following site:
philosophy.nd.edu/people/all/profiles/pl...
If that link doesn't work you can google plantinga supralapsarianism.
When I was attending Calvin College Dick Mouw, Alvin Plantinga and Nick Woltersdorf were teaching philosophy there. I was not able to work any courses by Plantinga and Woltersdorf into my schedule but I did take one with Mouw. That was, at the time, arguably the best philosophy department in existence.
I can't believe you brought this up. Most people's (except for some Protetant Reformed) eyes role back in there head and then they look for the closest exit if this subject comes up. While I wouldn't say that the infralapsarians won't get into heaven, I do think wrestling with the issue has increased my understanding of God and the universe.
In answer to your question, "Was solving the problem of sin the *primary* reason for the incarnation? Or does its primary purpose/meaning lie elsewhere?" I think the answer lies elsewhere. I think the primary purpose was to show God's love and glory more so than to solve the problem of sin. God created a world in which free will existed which allowed for the possibility of sin. Of all the possible worlds He could have created the one in which the incarnation would take place was the one that showed His goodness, mercy and love to the fullest possible extent.
I will defer to Plantinga for a fuller explanation of this.