Proof that Kenpachi is SaiGAR:
Let's say "P" is the power level of a normal captain. Normal captains can use bankai, but Kenpachi's power is at the bankai level even with his eyepatch on, so his power level is between 10P and 20P. If the eyepatch sucks a third of his power, that would put him between 15P and 30P when he's not holding back. Since he about tied with Ichigo, Ichigo should also be between 15P and 30P without any of his other power ups.
Since Ichigo can use bankai, that would make his full power somewhere between 150P and 600P. If we say that the difference between Noitora and Grimmjow is small, then Noitora should be about as powerful as Ichigo, somewhere between 150P and 600P.
I'm going to assume that the whole Arrancar/Vizard thing doesn't really do anything, since it doesn't seem to be doing anything.
Now, Noitora, who has a power level between 150P and 600P, is completely powerless against Kenpachi, who's somewhere between 10P and 20P since he still has his eyepatch.
This means that Kenpachi's SaiGAR makes him 15 to 60 times stronger than he's supposed to be.