Lovers vs. Friends

So it seems as though I've put myself in a situation that not only have I never been through before, but neither have any of my friends, or their friends, or anybody we could think of off the top of our heads been through. I'm talking about that, "I like you, but your my friend, but we'd make a great couple, but I don't want to ruin the friendship" situations. Long right? So my question is, when is it okay to just take a stand and say, "HEY! I want to be with you! So lets just be together!" or......is moving the friendship into a relationship even worth the risk of ruining a strong and close friendship. Many say that friends make the best companions but are those that say it really living proof?? I don't know; but times a ticking and I'm sure ready to find out.