Several of your sources are bullshit and invalid.
Originally posted by Schwarzenegger[/b]
"...Yoda could defeat the [b]most powerful Sith Lord in history."
-- The New Essential Chronology, page 84
Subjective, illogical.
Voren Na'al isn't able to compare Sidious' power to any of the Sith Lords' that preceded him, ergo his opinion cannot be used as a source. I would think the same applies to the Essential Chronology given the NEC is an update.
Empire's End(audio book i believe, i got this from nikkolas but hes banned now), one of the Ancient Sith spirits: "He gave up everything to the Dark Side long ago. He has become the greatest who ever lived. He is the strongest who ever lived....I say we give what he wishes."
Subjective, illogical.
Who was the spirit? How could he actively compare Sidious' power to others? If what DarkSerpent said was true (and it is), then it seems like some of the Ancient Sith were going to lay the smackdown on him. I don't see all of them holding the same opinion regardless.
Star Wars Insider, Kevin J. Anderson, upon asked if he ever intended his Sith to be stronger than the OT sith: No. Exar Kun, Naga Sadow and the others are on a firmly lower tier than Emperor Palpatine.
Blatant lie, idiotic.
Ignoring the stupid notion that's presented in that, this is an outright falsehood. Don't put words in people's mouths and expect it to hold any weight here, Schwarzenegger. You can't find the proof for this one because there simply is none. Lying won't help Sidious.
On TFN.net, official response to the strongest Sith: Palpatine at his peak.
Proof that this is official, not fan fiction?
Now shut up you kotor hardcore fanwanker.
I think I bashed GV back in the day, but he's quite clearly got a point now. So instead of Gideon's ass, perhaps you need to pull your head out of your own.