Too be honest I don't know they are obviously stronger than most of the Espada's that is certain but since we don't know much about the Vandenreich's abilities other than what Kirge has....had shown us. That old man gunslinger took out one of Shunsui's eyes without as much of a problem.
In the Winter War against the Espada's most of the Captain's began their fights without their Shikai active, but this time every single Captain and Lieutenant went into these fights with their Shikai's active. Yama-Jii's Lieutenant went Bankai against the Vandenreich on their initial invasion and ended up having it stolen and seemingly used against him.
Kira - Was able to fight against one of Luisenbarn's men and managed to defeat him, but this time he was OHK by one of the head Sternritter (possibly the leader of that group).
The main thing that interests me is who are the 5 the Vandenreich are worried about and can't steal their bankai's (other than Kurosaki)
But as for the question I saw most of them are possibly close to the power of Aizen (up to his crystallized form) Reason being is Kirge is obviously not as strong as the Sternritter group, A few of the Sternritters are easily overwhelming the captains (even if they stole the bankai's) and when you look at the fight with Kisuke + Yoroichi + Isshin vs Aizen, they couldn't stand up to Crystal Aizen (Although none of them went Shikai against him) While it took both Kurosaki and Urahara to take down Kirge even for a little while. It took mystery man to take Kirge out. So therefore the Vandenreich are close to Aizen level in power, well up to at least crystal aizen
That's a good observation.
Well , Ichigo outmatched Kirge in hes released form , without taking no effort at all , Ichigo as a Hollow against sternritters , Medium difficulty?