If you are planning on upgrading to Office 2007, and you want to be able to create IRM/RMS protected content, make doubly sure that you know what you are buying. Office 2007 Professional no longer has the ability to protect content.
You have to have Office 2007 Professional +. I know, I was surprised too!
Anyways, here is the link to what products have this ability with Office 2007:
I hope this saves someone the surprise of finding out a little too late.