Hmm, I guess Aizen could have been referring to himself there. I sort of rushed through that chapter when I first read it. Either way, Wonderweiss looks like he was a vastorode to start with, which, combined with his having been made with a boosted hougyoku, could make him the strongest of the espada currently present (except maybe ulquiorra)
Uryuu freaky, pale and geeky,
how do your powers grow?
"With gloves and scars and silver stars
and swords that I shoot from a bow,
yes, swords that I shoot from a bow."