I would say that, according to the markings you mentioned, and if you don't mind giving up the front and rear centers, you should be able to power the 2nd room speakers. The question is: How do you route the desired signals to those two amp channels?

Questions:
Is there a 'second room source' selector?
Is there anything in the manual about the terminals?
Is anything mentioned about 'second room' at all?
Are there any RCA jacks labeled 'pre-out' and/or 'pre-in'?

In some operating manuals, features that should be explained well in one paragraph can be spread out through the book in little snippets of info. My Sony digital camera manual, for instance, has two or three different page numbers for about half of the controls.

Larry
www.fineelectricco.com