I think it was just shy of X6 for that last storm. If I remember correctly, Oct 2003 was a couple around X20, they produced similar Auroras I feel.
The earth directed pay is so key though, fall might be good around the equinox. Something about the magnetic field orientation increases effectiveness.
I'm curious to see how 3664 looks when it returns in a week and a half. It looks like it popped off a backside flare, but showed up on coronagraph.