Changing Apple ID Email Address

Before iCloud came out, I had my personal email set up with my Apple ID. For security purposes, let's call this email "X."

Once iCloud came out, I made a new iCloud account (and thus, a new Apple ID). For security purposes, let's call this email "Y." To be perfectly honest, I don't remember what my reasoning behind this was.

I find it annoying, however, to have to remember two separate Apple IDs (one for iTunes/Mac App Store and one for iCloud).

Is there a way I can merge both of these Apple IDs into one? Ultimately, I would like to be able to use my iCloud Apple ID (email "Y") to download apps from the iStores, as well as to sync with my current iCloud email, Calendar, contacts, Photo Stream, etc.

Is there a way I can go about doing this?

Thanks! :apple: