Many people here must be new...anyways, besides the things that were hinted in the game Saix has been confiremd to be second in command thru translated scans before kh2 was released. He was always described as the "person who was seen as Xemnas right hand man, and second in command"...even the official website for 358/2 DAYS describes his character as second in command of the Org! This was translated from the heartstationwebsite also.
It also seems like SAIX is among the most powerful members in the Org besides Xemnas, and is spculated to be the second strongests member. Top members besdies Xemnas include, Saix, Xigbar,axel marluxia and xaldin...also lexaesu