I wanna do a bit of research and maybe come up with a rank system for the Sith. I'm still thinking that they have a crap ton of Acolytes, a handful of a ruling class, and then something in the middle. I don't know if the Lords are the ruling class, or if they are the middle and there's something above them. I'm thinking that you don't receive a title until being upgraded to the middle. I'm also thinking that the middle and the top classes have a set amount of each, and he only way to get up is to kill the one above you, or for them to die otherwise and you usurp their power. 

I think the Sith are and have always been a brutal and cutthroat order.