I have been trying to get Farkas from the companions to marry me. I have the Amulet of Mara on. I have completed the main Companion Quest line, but there is still not dialog that allows me to ask about marraige. Do I have to complete all the other radiant quests before my disposition is high enough?

Do you have the right Amulet of Mara?

I am not sure. The one that I have I got as a reward from a quest (Can't remember the quest name). It gives a restoration spell bonus.

Do you have to use the one the priest sells? I have found them as loot and thought to myself that I'll never have to buy one again.

I went back and get the one the priest sells and it worked.

I looted one and when I wear it I get the conversation option for Marriage, but have yet to use it. Does this mean mine won't actually work when I want it to?

I am doing the Temple of Mara missions right now and no one is giving me the option to buy a necklace, which I assumed was due to the fact that I already have one.

Moral of the story is, I'm fairly confident looted ones work, maybe?