How strong can he really be?

[Dansetsu]

I've been reading up on my chapters a few back, and I began questioning how strong Stark could really be as the No. 1 main espada of them all. I mean people were guessing that he was something of a strong guy, but no one really believed that he was top until we got a confirmation in the manga recently. So how strong can he be? He easily read Kyōraku's movements in seconds and found out 4 things about his fighting style that most captains can't find out. I don't think this is going to be an easy fight for him, even as the eighth captain of the group. I think even his bankai is going to get a good hefty workout. Plus we haven't even considered that if Ichigo with his hollow and his bankai is retarded for Ulquirra to fight (granted he had to release to handle him properly), then is the eighth captain's bankai and skill level higher? Should he have no trouble with Stark? And if Ulquirra released and he's only fourth, then Stark should be a beast of beasts.

Thoughts?