I always thought that he was Darth Sidious/Palpatine. Notice the similarity between the names Sipher-Diez or Sifo-Dyas (however it should be spelled, you know what I mean) and Sidious. It works out pretty nicely because, as you know, sidious is derived from insidious, and sipher-diez could be a combination of something that is both insidious and a cipher--thus...evil and unknowable. On Kamino, Obi-Wan is told that S-D (for short, er) ordered the army many years ago. Obi-Wan then muses that S-D was thought to have died 10 years before. While I understand that it is not impossible to become a Sith if not already a Jedi, the switch to the Dark Side seems much easier for those already trained to use and fight with the Force. It's easier to reject knowledge you have been given than to search and embrace the contradiciton of that knowledge yourself. I think, then, that Sidious was first a Jedi before becoming Plageius theWise's (again, not sure about the spelling) apprentice. The events that transpire in Episode I occur 10 years before those of Episode II. S-D could have ordered the army after having turned while using his Jedi name of S-D. He could have staged his death--taking on the dual roles of Palpatine and Sidious--becoming a senator in those 10 years before Episode II in order to ensure his eventual galactic take-over from the inside. He must have been the one to order the army because somehow "order 66" must be programmed into the clones that they know to kill Jedi--aiding in the take-over--when Palpatine/S-D/Sidious deems the time right.Lastly, I don't think Dooku is S-D becomes his Sith name is Taranus or Tyranus (makes more sense), and Tyranus is mentioned as visiting and checking up on the Kamino-cloning process after S-D has ordered the clones. Dooku/Tyranus would have checked on Kamino after S-D because 1) he wouldn't have known until he was told--as he didn't order the clones, and 2) he is Darth Maul's replacement and only falls to the Dark Side in those crucial 10 years between Episode I and II--and not before then.
