Yupp, like others have said, 85mm would be good for weddings I guess.
Since a wedding is a rather fast paced event, have you considered a zoom? They might not be as fast wide-open or give the best IQ (comparatively speaking), but they allow for a quick switch between focal lengths.
Since you use a crop body with 10-20 + 50mm, I think a good option is to go for the 70-200vr. If that's too expensive, and you don't really need the reach, I think that either of the 2 poll lenses will suit you. But since you have 80mm covered already, would a faster 85mm be of much importance to you (It might be, but I don't know what widest-aperture your zoom allows at 80mm).
Hope this help =)