skdutta, I'm sorry you haven't had an answer yet. I have the Sony 505, so I'll let you know what I do, sometimes.
If my DRM'd ePub book is already in ADE..
I open the Sony Reader Library and connect my 505.
I click the upper left "File" and on the drop down menu, I click "Import Files".
I click "user" then "documents" then "My Digital Editions"
<My ADE books are stored under user / documents / My Digital Editions on my laptop>
Then I just choose which book to import into the Sony Reader Library. Once there, I just drag and drop to the left pane to the connected Sony.
I hope I understood correctly and that this helps.