I'm not sure how Ajenti and OwnCloud are supposed to integrate. OwnCloud is actually fairly straight forward to set up. I'd encourage you to give it a try without using a panel. Often panels are more trouble than they're worth in my opinion. Since they try to hide things from the user, they often make things hard to debug.
Check out this article for setting up OwnCloud on Ubuntu:
OwnCloud is a personal cloud which can be configured to allow easy file sharing and remote storage, much like Dropbox. In this article, we will discuss how to install and configure this software to take advantage of a few of its rich plugins. We will also discuss how to mount a remote ownCloud share to interact with it locally.