I think it depends. Obviously, a husband is a much different type of relationship than a boyfriend/significant other.
If I was in a *new* relationship I would be completely unwilling to give up any friendships for a boyfriend. However, I would have to honestly say that I wouldn't risk my marriage and having a stable relationship with my husband for a friend. At the end of the day, my husband is the man I love and the man I plan on spending the rest of my life with so that relationship has to be more important than any of my friendships.
But here's the thing: if my boyfriend didn't like my best friend I doubt I would have ended up married to him since I wouldn't have sacrificed my friendship for a boyfriend. So I would have to assume my boyfriend and best friend had found a way to co-exist or I wouldn't have ended up married to this guy.
Now, if something were to happen after our marriage to cause my husband and best friend to dislike each other, I guess I would try to maintain both relationships but, like I said above, in the end I wouldn't ruin my marriage over it. I would hope, though, that my husband would be able to be undertsanding enough that I could maintain my friendship in some way. But, our friendship would probably change in some way.