I did exactly that a couple of months ago. It was as easy as just swapping the SD card over from the 505 to the 650.
I have to say that I didn't have any DRM infested books though. I guess you would need to make sure you have the new 650 authorised first if you do.
EDIT: Didn't notice the "no DRM" statement. You should be good to go!
Last edited by Bilbo1967; 12-07-2010 at 06:33 AM.